No, not at all.

Linear fighters, quadratic wizards is not just about DPS output; it’s really a terrible term the tier system improves on a little, see How are Fighters Linear but Wizards Quadratic? for commonly accepted definitions. It’s about breadth of options and things the fighter has no inherent answer to (fly, invisible, battlefield control spells).

PF2e makes little significant change from PF1e in this regard.

Of course, each class has its role so this is usually a pointless distinction anyway; in a PC party the wizard isn’t putting his time stop up against the fighters’ 5 attacks or whatever, they are synergistically bringing their own thing to the fight.

But in the way that the phrase is used, poor assumptions and all, it is just as prominent in PF2e as all D&D derivations.

Potentially, via Specialization

Disclaimer: this answer can change with the release of a single source book or errata, and thus can never be truly and permanently answered. Even without new material, this answer could change as understanding of the system grows. Also, formatting may be a work in progress (the links aren't showing well)...

TL;DR: The Fighter out damages the Wizard now (except at level 3), and thus a sort of balance is achieved via specialization - the Wizard specializes in versatility, and the Fighter in hitting things in combat.

What is the Problem?

It's important to begin the analysis with a thorough examination of what the Linear Fighter, Quadratic Wizard problem (hereafter LFQWP) is. The How are Fighters Linear but Wizards Quadratic? question has several great answers that cover the topic in depth, so I'll briefly summarize the criteria for comparison.

 1. Breadth of Options aka Versatility: how many options to respond to a situation does a character have?  2. Action Efficiency: how effective are a character's actions relative to other actions in the game?

It is important to consider that the problem is a problem because both of these factors exist. It isn't much of a problem if the Wizard has 80 ways to deal damage or incapacitate an enemy if none of them are as good as the Fighter's more limited ways. Thus, if we find that the Fighter beats the Wizard at either of these aspects, the problem is probably not severe enough to be labeled a problem.

Methodology of this Answer

This answer will examine the Fighter class and the Wizard class, as they represent the most idealized versions of martials and casters (respectively), and are also the problem's name sake. Additionally, the examination will attempt to look at a broad range of levels, with emphasis on the higher levels, where this issue becomes more pronounced.  

Fighters, Wizards, and Versatility

This first aspect of the LFQWP is that a Wizard is more versatile than a fighter. This, in a nutshell, remains true, although PF2e does attempt to add some baseline of versatility to all characters via Skill Feats. It is important to note that a Wizard via the Spell Substitution Thesis can have access to any spell in the Arcane spell list with enough gold, and can prepare it in only ten minutes. However, let's look at some details to show this.

Via Fighter Class Feats, the Fighter has several options for increasing versatility. Felling Strike allows a level 8 Fighter to make a two-action attack to bring down a flying enemy, very similar to the 3rd level spell Earthbind (available to a Wizard at 5th level). Blind Fight, another 8th level Fighter feat, can be roughly replicated by See Invisibility and Darkvision, both spells available to a Wizard at level 3.

At 14th level, a Fighter can grab the Determination feat. This allows the fighter to, once per day, remove a condition from themselves, or attempt to count a spell on themselves. The latter can be replicated by a Wizard's Dispel Magic spell (available at 3rd level, but it has to be heightened to display different levels of spells - a Wizard would have 7th level Dispel Magic available to them at this time, which would be the same counteract level as Determination). The conditional removal can be replicated by the Restoration spell, which is a 2nd level spell. However, Wizard's do not naturally get that spell (although it is achievable via archetypes, Trick Magic Item, and other methods).

At 20th level, a Fighter grab the Weapon Supremacy feat to be permanently quickened. Wizard's can grant quickened as early as 5th level via the Haste spell. At 13th level (a 7th level spell) that quickened condition can even be granted to 6 people!

In addition to all of that, a Wizard can breath water (3rd level), read minds (5th level), fly (7th level), grab a 20 foot burst of creatures (9th level), teleport (11th level), trap an enemy in a cage of force (13th level), turn into a Sea Serpent (15th level), instantly kill multiple creatures (17th level), and even stop time itself (19th level).

It's worth noting that a Wizard can hardly do these things constantly, as they consume spell slots. However, 3 or 4 times a day of many of these abilities is more than sufficient.

But what does the Fighter have uniquely going for it in Versatility? Oddly, the answer appears to be focused versatility. Fighter's get many abilities that a Wizard cannot replicate (nor would want to). Agile Grace allows a 10th level fighter to strike with incredible accuracy on their 2nd and beyond tasks; incredible potent when combined with their higher than normal weapon proficiency. Dueling Riposte allows an 8th level Fighter to strike back at an enemy that misses them, and Spring Attack allows a 12th level Fighter to move their speed and attack an enemy for one action. 20th level Fighters can even get a bonus reaction at the start of each enemies turn via Boundless Reprisals!

So, in summary of this section: a Fighter has less versatility as a whole than a Wizard, but has many unique options that align with the class focus of a Fighter ("unmatched accuracy and use [of] specialized combat techniques" - see Roleplaying the Fighter)). It's probably still correct to say this aspect of the LFQWP is still at play.

Action Efficiency

While it is difficult to accurately ascertain designer intent, this seems to be the area in which Paizo focused on fixing the LWQFP in Pathfinder 2e. The Fighter still cannot match the Wizard in incapacitating enemies (although other martials have better incapacitating abilities than the Fighter, such as Monk's Stunning Fist or a Rogue's Critical Debilitations), but incapacitation abilities in general were limited by the Incapacitation Trait, making them less effective relative to doing damage. 

But what about the Fighter's bread and butter, damaging things? For this comparison, we'll compare the average damage of a basic Greatsword Fighter to a Wizard's best single target damage spells' (Sudden Bolt and Disintegrate) average damage, both against entirely moderately stated enemies of the same level (using the Building Creatures rules from the Gamemastery Guide). The Fighter will have level-appropriate damage and to hit, assuming they are maxing their main stat (Strength in this case), and using the Automatic Bonus Progression - hereafter ABP - rules for simplicity, which are the basic equivalent of having the most up-to-date and level appropriate magic items). The Wizard will also max their main stat - at time of writing, they don't have any way to boost their Spell DC or Spell Attack with items, so we can safely ignore that. The Wizard will cast one spell (since that takes two of their three actions), while the Fighter will make 3 attacks (which is probably a less-optimal approach for a Fighter - they might be better off Demoralizing then attacking twice).

We'll examine levels 3, 5, 7, 10, 13, 15, and 20. 

Level 3

This is when a Wizard gets Sudden Bolt, and one level before the Fighter gets Striking weapons (Devastating Attacks in the ABP). Resultantly, this will probably favor the Wizard.

Wizard with Sudden Bolt: 4d12 (avg 26), DC 19 (T, +4 Int) vs Ref +9. CF 5%, F 40%, S 50%, CS 5%. (0.05)52 + (0.4)26 + (0.5)13 = 19.5 average damage. 

Fighter with Greatsword: 1d12 + 4 (avg 10.5), to hit +12 (E, +4 Str, +1 item) vs AC 18. Attack one: Miss 25%, Hit 50%, Crit 25%. Attack two: Miss 50%, Hit 45%, Crit 5%. Attack three: Miss 75%, Hit 20%, Crit 5%. (1.15)10.5 + (.35)21 = 19.425 average damage.

As expected, level 3 (barely!) goes to the Wizard. Now, the Wizard can only do this a few times in a day, but sometimes that is all you need. Now, the average damage of the Fighter increases by 6.5 next level, while the Wizard's remains the same, so it does seem to be a temporary and minor win for the Wizard.

Level 5

This is a huge level for Fighter. We've got Striking runes (Devastating Blows), and we've got a proficiency increase for Fighter. Let's run the numbers again, making sure to heighten Sudden Bolt of course!

Wizard with Sudden Bolt: 5d12 (avg 32.5), DC 21 (T, +4 Int) vs Ref +12. CF 5%, F 35%, S 50%, CS 10%. (0.05)65 + (0.35)32.5 + (0.5)16.25 = 22.75 average damage

Fighter with Greatsword: 2d12 + 4 (avg 17), to hit +16 (M, +4 Str, +1 item) vs AC 21. Attack one: Miss 20%, Hit 50%, Crit 30%. Attack two: Miss 45%, Hit 50%, Crit 5%. Attack three: Miss 70%, Hit 25%, Crit 5%. (1.25)17 + (.40)34 = 34.85 average damage.

The Fighter gets ahead here with a HUGE swing. Again, as expected; this was a huge level for fighters after all. 

Level 7

This is an interesting level; Wizards get 4th level spells and a proficiency increase, while Fighters get Weapon Specialization. Not sure who will take this one, but my money is still on Fighter given the lead they had at level 5. 

Wizard with Sudden Bolt: 6d12 (avg 39), DC 25 (E, +4 Int) vs Ref +15. CF 5%, F 40%, S 50%, CS 5%. (0.05)78 + (0.40)39 + (0.5)19.5 = 29.25 average damage. 

Fighter with Greatsword: 2d12 + 7 (avg 20), to hit +18 (M, +4 Str, +1 item) vs AC 24. Attack one: Miss 25%, Hit 50%, Crit 25%. Attack two: Miss 50%, Hit 45%, Crit 5%. Attack three: Miss 75%, Hit 20%, Crit 5%. (1.15)20 + (.35)40 = 37 average damage.

Fighter still wins, but by a narrower margin. Notably, the Fighter now has access to things like the Power Attack and Furious Focus combo, which would probably increase the damage even more.

Level 10

This level is big since we finally reach +5 modifiers. However, it's been awhile since the Fighter has had a damage boost. I expect things to be close again. Fighters will probably have some property runes that add extra damage (Flaming, for example) by now, and are hopefully using some feats to boost their damage in some way, but our basic Greatsword Fighter won't be doing any of that! Our Fighter does get a +2 item bonus now, though.

Wizard with Sudden Bolt: 7d12 (avg 45.5), DC 29 (E, +5 Int) vs Ref +19. CF 5%, F 40%, S 50%, CS 5%. (0.05)91 + (0.40)45.5 + (0.5)22.75 = 34.125 average damage. 

Fighter with Greatsword: 2d12 + 8 (avg 21), to hit +23 (M, +5 Str, +2 item) vs AC 29. Attack one: Miss 25%, Hit 50%, Crit 25%. Attack two: Miss 50%, Hit 45%, Crit 5%. Attack three: Miss 75%, Hit 20%, Crit 5%. (1.15)21 + (.35)42 = 38.85 average damage. 

Fighter is just barely above the Wizard (4 HP isn't a whole lot at level 10). 

Level 13

Fighter gets Legendary and another weapon damage die, and Wizard can cast Disintegrate (heightened to 7th level). Disintegrate is a bit tricky to calculate, since it requires a successful Spell Attack and then allows for a Basic Fortitude Save. Let's see what happens:

Wizard with Sudden Bolt: 9d12 (avg 58.5), DC 32 (E, +5 Int) vs Ref +23. CF 5%, F 35%, S 50%, CS 10%. (0.05)117 + (0.35)58.5 + (0.5)29.25 = 40.95 average damage. 

Wizard with Disintegrate: 14d10 (avg 77), +22 vs AC 33, DC 32 vs Fort +23. Attack: Hit 45%, Crit 5%. Save: CF 5%, F 35%, S 50%, CS 10%. Expected damage on hit: (0.05)154 + (0.35)77 + (0.5)38.5 = 53.9 average damage. Expected damage on crit: (0.4)154 + (0.5)77 + (0.1)38.5 = 103.95 average damage. TOTAL AVERAGE: (0.45)53.9 + (0.05)103.95 = 29.4525 average damage. 

Fighter with Greatsword: 3d12 + 9 (avg 28.5), to hit +28 (L, +5 Str, +2 item) vs AC 33. Attack one: Miss 20%, Hit 50%, Crit 30%. Attack two: Miss 45%, Hit 50%, Crit 5%. Attack three: Miss 70%, Hit 25%, Crit 5%. (1.25)28.5 + (.40)57 = 58.425 average damage. 

Again Fighter wins! I won't bother calculating Disintegrate for later levels, since it's not close to Sudden Bolt's damage. However, it's important to note that Disintegrate can benefit much more from buffs than Sudden Bolt, so in practice, it's not a lost cause in actual play, especially with things like True Strike existing! 

Level 15

Lots happen here; Wizards get Master Spellcasting and 8th level spells, and Fighter gets Greater Weapon Specialization! 

Wizard with Sudden Bolt: 10d12 (avg 65), DC 36 (M, +5 Int) vs Ref +26. CF 5%, F 40%, S 50%, CS 5%. (0.05)130 + (0.4)65 + (0.5)32.5 = 48.75 average damage. 

Fighter with Greatsword: 3d12 + 13 (avg 32.5), to hit +30 (L, +5 Str, +2 item) vs AC 36. Attack one: Miss 25%, Hit 50%, Crit 25%. Attack two: Miss 50%, Hit 45%, Crit 5%. Attack three: Miss 75%, Hit 20%, Crit 5%. (1.15)32.5 + (.35)65 = 60.125 average damage. 

Again, Fighter wins! I'm seeing a pattern...

Level 20

Finally! Who wins with everything on the table? Wizard has 10th level Sudden Bolt and Legendary casting! Fighter has 4 damage dice and a +3 item bonus! Everyone has apex items, which combine with the ability boosts at 20 to give a +7 modifier!

Wizard with Sudden Bolt: 12d12 (avg 78), DC 45 (L, +7 Int) vs Ref +33. CF 10%, F 50%, S 35%, CS 5%. (0.1)156 + (0.5)78 + (0.35)39 = 68.25 average damage. 

Fighter with Greatsword: 4d12 + 15 (avg 41), to hit +38 (L, +7 Str, +3 item) vs AC 44. Attack one: Miss 25%, Hit 50%, Crit 25%. Attack two: Miss 50%, Hit 45%, Crit 5%. Attack three: Miss 75%, Hit 20%, Crit 5%. (1.15)41 + (.35)82 = 75.85 average damage. 

Fighter still wins! The gap is fairly close here, considering the size of the numbers. That being said, Wizards don't get many 10th level spells (2 with a feat), so that's not much of a problem.

Summary

At basically every level past level 3, Fighters out-damage Wizards. This is before the Fighter even takes feats, and without factoring in critical specializations. Of course, as with any calculation, this has its limits. The Wizard does have a dangling third action, but they don't have much they can do with that that would affect the above numbers. So it seems that Fighters now do what Fighters are supposed to do; damage! While these numbers are generally close enough one cannot say that the LFQWP is totally and completely solved and irrelevant (the Wizard has incredible versatility while doing fairly close damage numbers), it does seem to have been reduced from the previous iteration of Pathfinder by making Fighters, appropriately, fighting specialists, and Wizards versatility specialists.

Yes.

I base this on my observation that people seem to mostly be debating "Casters are too weak in PF2" versus "Casters are OK as they are".

Examples of this:

https://paizo.com/threads/rzs436ao&page=1?Spellcasters-and-their-problems

https://paizo.com/threads/rzs42uui?Woefully-disappointed

The main mechanical reasons for this are:

(1) They get fewer spells per day.

(2) Enemies tend to have less weak saving throws, and many spells only have severe effects on a critical failure.

(3) It is almost impossible for a caster to win a battle in a single round. For example, spells that instantly knock out an enemy tend to have the Incapacitation trait, which means they don't affect higher level enemies.

(4) Utility spells are mostly weakened compared to previous editions, with short durations and the like.