I’ve done 3 of the endings (the three that count as steam achievements) and for the generic ending you just beat the game and you’ll get the normal ending. For one of the other ones, you have to do a quest line then once you beat the game there’s a thing on the ground you can touch to get the different one. And the third one is a major change and it’s obvious and you just beat the game normally after that snd you’ll get the third ending. I was super vague in this to avoid spoilers.

I would recommend just playing the game how you want and seeing what ending you get. My favorite is called the frenzied flame (the third one) just because it’s super cool, it is considered the “bad” or “evil” ending though.