I'm running Ubuntu Mate 20.04.3 on a GPD micro. It works pretty well. It's nice to not have to run the stockmind script myself.
I'm just curious, are there plans for updates for UMPCs? Is there a mailing list or irc channel development uses? The gitrepo linked from the umpc page hasn't seen a commit in a year and it has a dead link back to the ubuntu-mate website. Is this a dead project?
I would imagine that these hardware ports will only be created for the LTS releases, so you could probably look for the next LTS version sometime after 22.04 LTS is released, (that is often how it has been done in the past though not always) largely due to the extra effort that is required for the hardware ports, as the interim releases are only supported for 9 months anyway