I have to maintain a few UniFi Network Controllers, and I didn’t like to use the Web Frontend to update them. Especially because I have to use different versions for different installations. This is mostly based on the fact that for some, we have to use newer versions or even early access releases (they include fixes for issues).
Most of the installations are based on the UBNT UniFi Cloud Key (Gen 1 and Gen 2), or Debian. If you use another Linux distribution, you have to adopt it to fit your requirements.