Hello there!
I have been experiencing an annoying bug with GDM recently. When I'm trying to boot my machine, the PC stops at the Plymouth boot animation I set and doesn't switch to GDM.
There were no issues with this before the GNOME 42.3 update, but that just broke it. It probably broke when the init script for dinit (gdm-dinit) or any of its dependencies got updated (because dinit has automatic dependency checking for services).
If it's a bug, I hope the developers will fix it.
I have the same issue running runit. It's about 50/50 whether or not gdm will start.