It depends on what you would consider stable. I would install it alongside gnome for now and try it out. You can just leave it on your system getting updates while you use gnome and just pop in every once and a while. It’s up to you if you want to enable cosmic-greeter and disable gdm for your login page, but if you want stability, just stick with gdm for now.

COSMIC most of the time and then gnome as a fallback when I run into any temporary issues I can’t work around.

I do this with a custom bluebuild image I made that uses ublue (fedora 41) as a base and then added cosmic on top along with some other layers that I need/want.