I did a couple of big updates yesterday and I’m locked out of plasma now, I can enter the session but plasmashell isn’t starting (neither Waylan nor X11).
I see KWin is running because overview opens and there’s an input box (Krunner or alike) where I can search and try to launch apps, like xterm. Krita opens but it seems to be the only one KDE app I can open now.
Overview opens either from hotkey or screen corner, and I can also see some desktop effects working.
I can’t open Chrome in that session, but it dooes work from the non Plasma sessions.
Inspecting the update logs I see it upgraded Qt6 to 6.7.0 from 6.6.3 but I did some tries to revert it, but apt doesn’t find it (or I’m failing there).
If I try to launch plasmashell or konsole form (u)xterm, I see coredump and KCrash, but the coredumps aren’t usefull without the dbg symbols packages installed (well, if anyone knows a oneliner or has a little script to get all of them installed for the installed packages I’d try).
The problem with Qt is that you can’t upgrade the library and continue to run applications built against the previous version - even a minor certain charge - which is not how most libraries work.
Because in almost every other case upgrading a minor library version does not cause issues, the automatic package dependency management will let you upgrade even though it does break the system.
The Neon packagers should make sure to lock the exact Qt dependency in their packages, but because the dpkg build tools do not know how to handle Qt, this is a lot of manual work that can’t been done.
You should either downgrade Qt to 6.6 (it is very much not an easy thing to do, but I can probably walk you through it) or rebuild the apps you need to work with Qt 6.7 (which would maybe be easier, but not by a lot) - until Neon completes the move to 6.7 by rebuilding all the apps.
