They exist, for example SteamOS has closed source desktop shell based on Steam client
replyTheir gamescope compositor is free software at least.
replyWas it Caldera that shipped a linux with Motif?
reply(We're talking three decades ago now)
fwiw I can remember all the turmoil when Qt had no free tier and KDE was work of the devil
replyIf you or anyone else want a trip down memory lane around that topic, peppered with some interesting revelations, this video is worth checking out:
replyKDE: The Documentary — The Story of Free Software Underdogs