@pointlessone
Pleroma — works fine on my olde PowerPC G4 MacMini with only a gigabyte of RAM.
GoToSocial as others noted, I don't have experience with it, but I heard good things. You need hardware that is supported as Go target, PowerPC doesn't cut it.
Honk — if you're really-really-really into minimalism.
And if you are also interested in Gemini, there is Tootik.
Sorry for not providing links — 500 char limit, I think you can look all those up easily.