again, most of that is handled by the package maintainers for any particular distro (ex. for Guix, gnome-shell and plasma have already been taken care of)
a lot of packages don’t touch or even know about the init system
so the worries will only come into play for packages not in the chosen repository AND require systemd – and for distros not using systemd, they’ve probably already got a process in play for translating between systemd and whatever they’re using