Hi, gentoo&alpine contributor that saw this bug on IRC so not a debian point of view but a warning:
As seen in [1] regarding the headers, sdl12-compat isn't a full replacement yet. It could work for pure binary-compatibility but you can't build anything against it yet so it should be a Provide+Replace rather than something like a newer version. 1: https://github.com/libsdl-org/sdl12-compat/issues/34
