Skimming through my browser history:
- https://hmnafterall.itch.io/echochess
- https://hellolorem.itch.io/kings-court-chess
- https://threethan.itch.io/chesscourtquest (This one is a little different because pieces aren't removed, and your goal isn't capturing but moving the king to the flag, but it does have the "become the piece you capture" mechanism)