Ah.
I thought they had actually finally finished COSMiC?
Apparently not?
Back 5 ish years ago, I was able to run Steam and the Index on it, back in Proton 6/7 days, via installing Steam from Debian sources.
(obligatory acknowledgement of meme numbers)
Hell I had RDR2 working on it, even online worked up untill the point Rockstar decided all linux gamers are hackers.
Anyway, back when it was their sort of modified version of GNOME, I quite liked it, because it was both easy for newbie to understand the basics, but also allowed significant customizability and tweak ability for more experienced users.