Get someone to take care of the cat while you are away. Either relatives, friends or some kennel/petcamp. You will feel better knowing the cat is in good hands if it's condition should worsen and the cat will feel safe.
I'm not a Kubuntu expert or even user, so I will just list op the general steps.
Boot into the live USB and unlock the encrypted drive. Make sure you have an internet connection too.
Then chroot (change root) into the OS drive you decrypted and look at the logs from last update or even boot logs if posisble to determine what went wrong during the update.
If possible fix the issue and complete a full update again (apt update & apt upgrade). Hopefully that should fix it.
Does your PC have any known hardware that requires proprietary drivers, like Nvidia or Broadcom?
Just to clarify. You system is not bricked. Bricked means that it can't boot anything. It sounds like the update is not working correctly (eg the kernel is not fully loading).
You have two options:
Try to repair the current broken install (can be difficult depending on skill level)
Backup your data and "nuke'n'pave", eg re-install it all.
Both options require a live USB with your distro on it (preferably the new version).
understand why this post has such a negative vote count when the conditions for its existence seems like an acceptable risk since it’s disconnected from the internet;
The OP says nothing about being disconnected from the internet. The referenced guide uses a computer without internet, but not OP.
So it's fair to assume OPs PC is still connected to the internet, as must devices are these days.
I had something similar happen in Plasma 6.1 and 6.2. After I turned off the dccutils support in powerdevil, I have not had the issue since. My desktop is not a laptop, so it's always powered, same with screen, so I don't need fancy power profiles.
I'm on the latest episode now. Boy, the first couple of episode was rough, audio wise. Much better in the later ones. Do you ever plan on having guests or even co-hosts on the show?
I like when there is banter and discussion between people on podcasts. Makes it feel more organic. :)
Ah, my bad, forgot about the threads thing. :)