change hostname using GUI

Has the GUI changed that much from 11.6 ??? In 11.6 go to System -> Platform

Keep in mind that this wont' change the hostname in your device certificate.

After you logon to the F5 GUI

System > Platform > Host Name (filed that you can change it)

So it will change in both GUI and SSH

Login to the F5 device GUI via a browser (use administrator account to login). Once logged-in see the list of section on your left side. There follow the below

System > Platform

Once you select Platform a screen will open where you will see the Hostname field. Change it to the desired value and go down and click update.