apt will brick itself if it gets interrupted mid transaction with no clear recourse apart from a total reinstall, so try not to get greedy and Ctrl+C if it looks like dpkg is hung
You can dpkg -r the package you tried to install then apt won’t complain about missing dependency packages for your app as it won’t be marked for to be installed
trying to install any software that isn’t already packaged explicitly for Ubuntu is a nightmare because there is no equivalent of the AUR for people to push build steps to and you’re quite often left guessing what dependencies you need to install to get something to compile
There isn’t a big global community repo per say like aur but anyone can host their own repos with PPAs, you just need to add them to your lists
Most apt quirks are there with Debian too, not just an Ubuntu thing. The rest of the things you mentioned are fair.