Black screen after login into Plasma

Have used Kubuntu for a few years now but have now somehow broke my OS. I believe I ran some commands to stop and start my plasmashell before rebooting which may have been the cause of this.

Before login if I select my normal “Desktop Session: Plasma (X11)” or “Plasma (Wayland)” then a black screen appears when I log into my user.

If I instead select “Desktop Session: Ubuntu on Xorg” then I can load up this desktop and run most apps, though Settings and some other system ones don’t seem to load. I’m quite unfamiliar with this desktop environment but presume it’s GNOME.

In Plasma I’m able to CTRL + ALT + F3 into tty3 but I’m not sure what commands I can use to resolve this.

PC: XPS 13 (2019?)
OS: Kubuntu 23.10

do you have a nvidia GPU?

the best no fail update procedure is

sudo apt update
sudo apt purge *nvidia*
sudo apt autoremove

and then re-install the proprietary drivers again only after every thing else is working again on the nouveau drivers.

No, the XPS 13 uses an Intel iGPU.

can you boot to a previous kernel from the grub menu (under Advanced)?

In the end I created a new test user and used rsync via tty to copy my primary user’s files to it, removing directories and files from the test user whilst logging on after each change to see what exactly triggers the error.

I determined that ~/nix-profile was causing it, so it’s something to do with my Nix packages/config. Not sure how exactly to debug that further at the moment but now at least I’m able to log on, albeit without my Nix packages.

No great loss as I just commented in another thread junk software that messes up my computer gets deleted and never installed again. And again it involves supposed secure software, first comment was on password manager hijack of desktop, now this and their supposed best software manager idea that trashes the entire desktop in its operation…