ubiquiti-unifi-controller is built for Intel macOS and so requires Rosetta 2 to be installed.
You can install Rosetta 2 with:
softwareupdate --install-rosetta --agree-to-license
Note that it is very difficult to remove Rosetta 2 once it is installed.
Installing ubiquiti-unifi-controller means you have AGREED to the license at:
https://www.ui.com/eula/