How to approach this Knight vs Bishop endgame? Black to play.. Whats your eval?

This is probably zero-ish if you're an engine, but I'd always take a bishop in such a positon. Easier to play.

If we can stabilize the position, black should be better. There are pawns on both wings and black has the bishop, while white has the knight. These endings could be enough for a win. The main problem for black in this position, however, is that he's a bit behind in time and activity. We need to be careful of Nd6-c8 for example. And another problem that we could face is for example 1. ... Bg3, 2. Kf3, Bc7; 3. e4, fxe4; 4. Kxe4, Kf7; 5. Kd5 and the white king is so active that we're in trouble. There's also the idea of 1. ... Bg3; 2. Kd3, Kf7; 3. Nd2, Ke6; 4. Kc4 taking advantage of the weakened black queenside. So the concrete evaluation of this position could be based on tactics. In practice, at the moment it's a real battle. Both sides can't afford to slip up. If white can't make something happen before black catches up in activity, black will have the better chances. I'd have played on with black, as I think black should be able to neutralize white's play with something like 1. ... Kf8.

A draw. No possible progress.

Draw but easier for White

How to approach?

It's all about piece activity. I look for ways my king and minor piece can "touch" weak pawns, and the same for my opponent.

One of my first questions was "if white plays Nd2 plus a4, what is my winning idea?"

After a quick think nothing is coming to mind... having said that, it's sometimes dangerous to try a fortress so early. Knights love to dance around and harass pawns in the endgame. So like I said earlier, I also noted squares I might dislike a knight landing. c8 is an obvious one.

Also, the endgame (IMO) is a lot like the other phases in the sense that you maximize piece activity before thinking of changing the structure or opening lines with pawn breaks. Maybe some of the better players who comment can tell me that's too general or even bad...

... but keeping that in mind, another thing I think of is if the pawns stay where they are, obviously my bishop+king can't overwhelm and win any single pawn. So what has to happen eventually is a pawn break like b4, f4, or even g4. Just something. Then ideally I can infiltrate further, or damage white's structure and tie a defender to a weak pawn, or make a passed pawn to tie a defender to blockade it. This is the (very general) winning process of many positions, not just endgames.

I like your analysis but this is a position where both sides can't really make progress. That said it's easier to play White here as he can 1) basically never lose and 2) set up a blockade on the light squares

I'm not saying I'd play this particular position for a win... but I think it's a very useful thing to talk about, because a lot of lower rated players (or inexperienced players) start making very strange moves in the endgame when in reality the core ideas aren't so different from the opening or middlegame. If the OP understood the general ideas, then it would help him do things like win equal endgames vs lower rated players.

I don't know, maybe I just like talking about stuff like this.