[throwaway82652]

>Just take a look at GDM meson build script and you'll see: systemd_dep = dependency('systemd') libsystemd_dep = dependency('libsystemd')

This is only required to build it, not run it. It should work fine with elogind as a drop-in replacement, since elogind is API compatible.

>Although it seems fine to have systemd as an option, it's ridiculous to have it as a hard dependency.

No this is wrong, it depends on logind for a very real reason. Managing the seats isn't secure without logind or similar functionality. If they supported operating without that it would compromise security. And if you're on a single seat system and really don't care about security, you might as well disable logind and gdm altogether, and launch your user session straight from the VT.