So I'm stuck with Ubuntu LTS on workstation from my employer and cannot do anything about it due to policies/enrollment software. I will be able to update to 24.04 soon, but it doesn't help much, as it ships Plasma 5.27 - which isn't bad, but there's a leap of features and general polish to the new Plasma that really shines on more up-to-date distros and fixes some annoyances.
And honestly, LTS gets old so quickly that I have to go to external sources like Flatpak, Homebrew or Nix for fresh stuff anyway. That Ubuntu install is then thin underlying OS that stays the same for a long time. Even 22.04 is then fine for some years to come.
As for the build, I used kde-builder (kdesrc-build) and jump through a big pile of hoops with dependencies. I needed to manually compile some of the required libraries that were either too old or missing. I downloaded Qt from the official website in the most recent stable version. When all is properly set and done, it works like a charm, just like on my other(archbtw) box.
If there's some interest I could try and put together what I discovered in a form of something like tutorial, but that would be a lot of work for an info that's useful for just handful of people. Anyway, if you try to do it yourself, feel free to ask questions if you're stuck on something.
Windows on external USB drive, disconnected after each use