Mais ou menos resolvido, não consegui reverter para a área de trabalho padrão, então baixei o 17.04 em outra máquina, criei um pendrive de inicialização e fiz uma nova instalação na máquina afetada, obrigado mesmo assim, Phil.
Eu fiz o upgrade para o 17.04 e escolhi o Gnome no Wayland. tela ficou em branco, eu finalmente desliguei e liguei novamente e agora tenho uma tela 'terminal' mostrando:
Ubuntu 17.04 phil-fujitsu tty2
phil-fujitsu login:
What do I need to type to get back to the standard Ubuntu display?
Ctrl Alt F7 gives me:
/dev/sda2: clean, 349106/19251200 files, 18428478/76998912 blocks
[ OK ] Started udev Kernel Device Manager.
Starting Remount Root and Kernel File Systems...
[ OK ] Started Remount Root and Kernel File Systems.
Starting Flush Journal to Persistent Storage...
Starting Load/Save Random Seed...
Starting udev Coldplug all Devices...
[ OK ] Reached Target Local File Systems (Pre).
Mounting Mount unit for nmap...
Mounting Mount unit for core...
Mounting Mount unit for core...
Mounting Mount unit for nmap...
Mounting Mount unit for core...
[ OK ] Mounted Mount unit for core.
[ OK ] Mounted Mount unit for nmap.
[ OK ] Started Flush Journal to Persistent Storage.
[ OK ] Started udev Coldplug all Devices.
Starting Show Plymouth Boot Screen...
[ OK ] Started Load/Save Random Seed.
[ OK } Mounted Mount unit for core.
[ OK ] Created slice system-systemd\x2dbacklight.slice.
Starting Loas/Save Screen Backlight Brightness of backlight:acpi_video0...
[ OK ] Mounted Mount unit for nmap.
Obrigado, Phil.