Cannot log in - KDE manager cannot load theme

Ubuntu 24.04 + KDE Plasma. I picked a new login theme which apparently was defective. When I rebooted there is a message that the current theme cannot be loaded. There is no login box, so I cannot login and choose a new theme. Is there a way to boot using a “safe” theme, or some way to bypass the login window? There is an error printed:
Any-Light-SDDM-6/Main.qml Library import requires a version.

If you switch to a tty you should be able to start plasma.

I think the command is startplasma-wayland

Thanks for the suggestion, but I’m not sure what you mean by “switch to a tty”. I tried booting in recovery mode and dropping to a root shell which is the only tty I can think of.
However, I don’t know the root password since I’m using a computer supplied by my university, so I cannot get into the root shell. Is there some other way to get a tty?

  • Start your laptop normally until you are at you broken login screen
  • Press CTRL+ALT+F3. If that doesn’t work try a different F Key
  • Login using your username and password
  • Type startplasma-wayland and hit enter.

Now you should be logged in.

Thanks for the prompt answers. For me CTRL+ALT+F4 worked to get a login prompt. To run startplasma-wayland I had to install a package, which luckily I could do because I have sudo privileges. I then foolishly tried installing another theme which did not work, so eventually reverted to a previous one which worked. Thanks for help with this problem.

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