So this is my understanding:

Danganronpa 1 is basically the same as the anime

Danganronpa Ultra Despair Girls takes place between 1 and 2 but should be played after 2 because it spoils 2 (Can I skip it altogether?)

Danganronpa 2 takes place after Ultra Despair Girls and has no anime

Danganronpa 3 (game) has pretty much nothing to do with the rest of the series, games or anime

Danganronpa 3 (Anime) half takes place before and half takes place after the first game/anime, but you need to know the story of 2 for it to make sense?

I'm not really concerned about any visual novels or manga or whatever is in the series, unless it's 100% critical to understanding the story of the games. I know there is a VR demo of a trial from the first game(?) but I don't think it matters? I'm not sure if there are any other games I'm not aware of.