For info for you and all users:
If you go to openmandriva.org select the Download button, select Spins you get to this:
Read this text, all of it! This was written for a reason.
Scroll down to:
All users please note that the primary focus of OpenMandriva at this time is Plasma6 then Gnome and LXQt. That is due to resource allocation not lack of desire. Of the others listed there XFCE isos will work with the workaround posted above. Do not know about Mate. Currently Cinnamon, and Budgie do not work.
It is reasonable to use ROME Gnome or ROME LXQt for production, ROME LXQt should be regarded as Beta. Any of the rest of this is Alpha.
Edit: I just noticed that @AngryPenguin posted this workaround for Cosmic iso.