2) sudo apt remove unifi

3) sudo apt auto-remove (optional, this is to clean packages that are not in use)

4) sudo vim /etc/apt/sources.list (or use your favourite text editor)

At this point, you should see your previous one: deb http://www.ubnt.com/downloads/unifi/debian stable ubiquiti

Replace the word STABLE for UNIFI5. Now it should be like this: deb http://www.ubnt.com/downloads/unifi/debian unifi5 ubiquiti

Exit and Save

5) sudo apt-key adv --keyserver keyserver.ubuntu.com --recv C0A52C50

6) sudo apt update

7) sudo apt install unifi

Login to your local Unifi portal and you should have version 5!