Doesn’t have too! You can just use nix as a package manager and install it to whatever distro you choose 😉

Uhhh, there are no alternatives to SystemD right now.

While different inits exists and they work just as well as SystemD, there is no replacement for the whole suite of programs.

See PostmarketOS, they ended up adding SystemD because it ends up being either thar or reinventing the wheel.

Imho SystemD gets a lot of hate for no reason at all. (Not saying it is perfect at all).