There are only a few times where the only condition is incapacitated

The Arcane Archer's Banishing Arrow states:

While banished in this way, the target's speed is 0, and it is incapacitated.

Both the banishing smite and banishment spells state:

While there, the target is incapacitated.

The symbol spell states:

Pain. Each target must make a Constitution saving throw and becomes incapacitated with excruciating pain for 1 minute on a failed save.

The wind walk spell states:

Reverting takes 1 minute, during which time a creature is incapacitated and can't move.

The Tomb of Levistus Eldritch Invocation:

[...] you gain vulnerability to fire damage, your speed is reduced to 0, and you are incapacitated. [...]

The Short Term Madness table in the DMG states:

21-30 The character becomes incapacitated and spends the Duration screaming, laughing, or weeping.

The Wild Magic Sorcerer's Wild Magic Surge tables states:

41-42 You turn into a potted plant until the start of your next turn. While a plant, you are incapacitated and have vulnerability to all damage. If you drop to 0 hit points, your pot breaks, and your form reverts.

And the Unearthed Arcana Raven Queen Warlock's Sentinel Raven feature states:

While perched on your shoulder, the raven can't be targeted by any attack or other harmful effect; only you can cast spells on it; it can't take damage; and it is incapacitated.

Most of these either make the target go to another plane of existence or they affect the player character and not a target. The only one that could be used offensively is the symbol spell's Pain option.

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There aren't even very many ways to apply the incapacitated condition with other conditions, which, as user @thedarkwanderer pointed out, would inflict only the incapacitated condition if a monster were immune to the other condition.

The Tasha's hideous laughter spell which inflicts the prone condition:

The target must succeed on a Wisdom saving throw or fall prone, becoming incapacitated and unable to stand up for the duration.

And finally the feign death spell which inflicts the blinded condition:

The target is blinded and incapacitated, and its speed drops to 0.

The Pain effect of the symbol spell inflicts incapacitated and no other conditions.

One of the options I can choose for the symbol spell (PHB 280) is:

Pain. Each target must make a Constitution saving throw and becomes incapacitated with excruciating pain for 1 minute on a failed save.

While it lists the inconvenience as described in Ben's answer, it does not inflict any other conditions, mechanically speaking.

Maybe I should have looked harder before asking.