Hello,   I have the same issue on 7060 and 7070. No problem installing Ubuntu 20.04 and reboot. But once all updates are installed, I'm stuck as you here. To bypass you need to restart GDM via ssh : service gdm restart  You need to do it every time you reboot... I don't have more informations on why it is not working... Maybe open a ticket on Ubuntu Support ?   Best regards
I have just installed the latest version of Ubuntu on my new Optiplex 7070 SFF (clean install). After installing, I  installed the updates in Ubuntu, but after restarting it got stuck on the startup screen (picture included). Nothing works, none of the buttons work F2, F12, ctrl-alt-del... Any help is appreciated. [IMAGE]
Optiplex 7070 SFF - Stuck on Dell screen after Ubuntu update