I have a similar problem with Plasma 5.27 on Wayland. Hibernation is just broken and shutting down takes about two minutes…
I’ll check if the same issue is on X11. We might be having different issues with the same symptoms. The journal showed Wayland and other issues as well. Hmm… I won’t post my log here for the time being, so I would not highjack the thread. I’m curious if some similar issues will come up and about the methods of solving such a issue.
EDIT: I checked X11 session and the issue is gone, so my problem in Wayland specific.
EDIT2: I found out that this is a SDDM (upstream issue) and they have been notified about it. It’s unclear when they will fix it. See the details:
https://bugs.kde.org/show_bug.cgi?id=445449