Cataclysm: Dark Days Ahead isn't really indie, it is straight up Open Source and a freaking good roguelike. The DDA variant focus heavily on the realism aspect of survival, but there are forks that try to gamefy it more.

There is also Rain World, which I am addicted for 3+ months now. It is also on sale, but before you buy it, know that you are going to die A LOT, but it really isn't a big issue; it's actually funny most times lol. Great lore too.

And one that I've rooted for a long time and I think flopped hard in its release is Below, but I very much still love it.

Also, one that I played for a bit last week and the soundtrack slaps hard is APE OUT.

How did I forget about Noita? This one is a masterpiece. Crafting a wand just to fucking obliterate yourself out of existence .3 seconds later is just chef's kiss. Also hämis.