I just downloaded the most recent ISO for Plasma and installed it under VirtualBox.
Try this:
Start Konsole
Open Settings
Manage Profiles
Create a new profile, set it as default.
Close app, restart … and there’s only the built in profile.
Spend 15 to 30 minutes poking at this problem.
Maybe it’s something else that’s supposed to go in a magical declarative declaration file thingy. Google results show answers to problems I don’t have and refer to utilities that are not included in the current version of the OS.
Dink with it some more.
And suddenly the creation of a new profile has stuck. Is this because I have a section in /etc/nixos/configuration.nix for the profile? Nope, I move on to doing other stuff and nixos-rebuild switch fails because it’s there.
So I’ve faced this a couple times now as I’ve just started using NixOS, it’s reproducible, but fixing it? shrug
Theoretically it should be easier/more stable to use a system configured in a declarative fashion. In practice things that take sixty seconds on other Linux distros require an hour or two with Google and ChatGPT.
And that is NOT a benefit …