Your line is fine again. I might be raising the turn as their 50% pot bet doesn't really scream strength and I'm not worried too much about getting raised either since they have been betting fairly small.

River check with the intention to call is fine, in hindsight it would have been nice to donk.

Pre: Vs an UTG opener I think calling here is fine to keep their range as wide as possible. I wouldn't hate a three bet but I'm not going to argue strongly in favour of either or.

Flop: Check calling seems best to me on this board. Donking makes little sense with such a strong hand and I think check raising accomplishes nothing as we will fold out an absolute ton of hands that we have basically drawing dead.

Turn: I would be tempted to stick in a raise here after our check when we pick up the nut flush draw. We have a ton of equity and ca extract value from hands like KQ here by raising. Again though I do not mind checkcalling by any stretch though.

River: Our choices here are between check calling and donking out, my preference would be to check call as played or else donk really small to try to induce a bluff raise. Either way we are targeting the same types of hands, his 0 equity showdown value hands which I would guess will make up a decent part of his range here. If we bet small, as in super small (around .05-.10c) then he may opt to bluff raise as people hate folding to these tiny bets, but trying to induce a bluff by checking seems reasonable too. Donking large here does not make much sense to me as we are specifically targeting a hand like KQ and that is about it so we are not getting a huge amount of value.

I like the idea of raising the turn. Villain wouldn't likely be betting so small with a powerhouse hand, but he's also never folding Tx with a pair. Another benefit of this is that if we do bink the flush then we avoid having to donk the river, and we will also be betting into a bigger pot increasing value.

If villain had bet the river I wouldn't be comfortable calling. 2NL players just don't 3 barrel bluff enough, and his small bets can believably be 9x. It is exploitable but I would never expect that to matter much at these stakes.