There is something magical about asking Ubuntu to upgrade your desktop while you're running it. "Hey, Ubuntu, let's try focal" and it heads off to churn through downloading 6GB of stuff and unpacking/installing it. You head off to work in the meantime.

But it gets stuck because you have postgresql and it doesn't make it clear that what it wants you to do is to do a pg_dumpall, then uninstall postgresql-* (and timescaledb-*) and then re-run the upgrade. Okay, that's annoying, but whatever. You do that, and the upgrade goes back to churning, but gets stopped half a dozen times to ask if you want to overwrite files... well, I was sitting here working anyway, so oh well, but I would have been annoyed if the process had sat there for hours waiting for a prompt instead of continuing the work.

Oh, but you forgot. You needed to open gnu-cash to call the government for a due-date... it isn't going to work half-installed. Oh, and file-save dialogs in MSCode won't work either, because they're OS-provided and are in the middle of being replaced... so... this was not a good plan.

But in the end, the upgrade only takes 2 hours, so accept that even magic has its limits and you should likely not expect to get too much work done while the machine is upgrading.

[Update] and, honestly, when nvidia drivers wind up un-installed after the upgrade, but the X server doesn't fall back to using native... that kinda takes the shine off too.