user @Juest reported a problem with xdm-openrc (https://gitea.artixlinux.org/packages/xdm-openrc/src/branch/master/xdm.initd) . as he said the service is unusable as it is.
as reference I can look at xdm-runit (https://gitea.artixlinux.org/packages/xdm-runit/src/branch/master/xdm.run) or original systemd service (https://gitlab.freedesktop.org/xorg/app/xdm/-/blob/master/xdm.service.in?ref_type=heads) .
I'm not familiar with writing openrc service but I think all that lacks is:
command_args_foreground="-nodaemon"
this line has been used by other openrc services (https://gitea.artixlinux.org/packages/cronie-openrc/src/branch/master/cronie.initd) that artix uses, but I couldn't find it in service-script-guide (https://github.com/OpenRC/openrc/blob/master/service-script-guide.md)
I confirm this work, whenever I get the time to spin a virtual machine.