I just installed KaOS after a long time, I like all the progress you made and thanks for cool distro using technologies I like (I code with Qt). Switching from Arch, hi.

Now, I've used Croeso to install Firefox and that was the first thing I did after initial reboot. It has run full system update with it (166 packages) but get stuck on 6th and final step: "updating the MIME type database". I've googled that the latest shared-mime-info package can cause that because it runs for every package separately. I was okay with waiting... but it's been an hour now. Should I keep waiting? Will it eventually finish or is it a separate issue? Is the solution on Arch's forum compatible with KaOS?

I'm running the OS on Intel NUK and it's a low-end system so I'm not ruling out that an hour just wasn't enough.

That looks like a bug with the shared-mime-info hook:
https://github.com/KaOSx/core/blob/master/shared-mime-info/update-mime-database.hook
Though strange that no-one has encountered it (last change was from May this year).
If you are sure the rest of the updates were done, just hanging on last part, running hooks, then it is safe to stop the update.
Can you post the pacman log before rebooting, just to make sure?
/var/log/pacman.log

Does manually running the hook command also hang your system?

sudo /usr/bin/update-mime-database /usr/share/mime

it doesn't react to ctrl+c, I was just getting the ^C so I've just closed the Konsole. Nothing wrong in the log, just last entry is running the hook. I've copied it if you want the whole thing but nothing there.

Just to be clear, my system didn't hung, just the process didn't finish. Running it manually works and was instant, then there was nothing to do for pacman -Syyu so it's okay now I guess... thanks. Will report if it happens again.