For me it installed manually OK, but does not see devices on network and cannot adpat using mobile application either, dunno where could be problem
sudo apt-get update && sudo apt-get -y upgrade
sudo apt-get -y install oracle-java8-jdk
echo 'deb http://www.ubnt.com/downloads/unifi/debian stable ubiquiti' | sudo tee -a /etc/apt/sources.list.d/100-ubnt.list > /dev/null
sudo wget -O /etc/apt/trusted.gpg.d/unifi-repo.gpg https://dl.ubnt.com/unifi/unifi-repo.gpg
sudo apt-get update
sudo apt-get -y install unifi
sudo systemctl stop mongodb
sudo systemctl disable mongodb
My bad, I did not understand UBNT, you can adopt devices only if they are not setup without controller (or with other controller obvs.)