Huge update - can't log in

[Duha]

Check this thread, maybe this is also your issue?

Plasma 6 update, desktop won't load

I just had the same problem with my neon. I had to do an : sudo apt autoremove sudo pkcon install libdecor-0-0 sudo pkcon install libsdl2-2.0-0 sudo pkcon install plasma-desktop sudo pkcon install plasma-desktop-data (before that I removed VLC but dit not remember if it was with apt or pkcon )