Katana Zero will be THE indie experience for me. Oc Binding of Isaac, Hollow Knight, Dead Cells are also perfect.

Im checking my library atm and I can also recommend: Bloodstained Cuphead Deaths Gambit Forager Sifu, one of my personal favourites Slime Rancher Wuppo

I think you mentioned Celeste, thats a great platformer too.

Hope you have fun with any of these as much as I did