Is it a touchdown if the receiver puts a knee out of bounds before the second foot in bounds?

In the NFL then, no, both feet always need to touch in bounds while the receiver has possession. Once any part of the body touches out of bounds the play is immediately dead so anything that happens after that instant doesn’t matter.

Section 2, Article 7: Player Possession

Now for a reception in the NCAA the point is irrelevant as the rule is you only need to establish one foot in bounds while maintaining possession.

Section 4, Article 3: Catch, Interception, Recovery