Here I quote Gary very liberally:
This is how I got Ubuntu to work:And scene. Gary adds he has to boot into rescue mode as it seems necessary with the nvidiafb and it's the only way to have shutdown, suspend, and reboot working properly. He also likes MATE, and after playing with the latest release on my Debian Sid install, I like it, too. So there.
Download Ubuntu 16.04 minimal install iso for ppc.
Install system utilities and Ubuntu Mate
When finished, reboot
At yaboot type: Linux nomodeset single
When you reach root, type: visudo
Below: root ALL=(ALL:ALL) ALL type: username ALL=(ALL:ALL) ALL (as per your instructions)
Hit Control o, hit return, then exit
nano /etc/modprobe.d/blacklist-framebuffer.conf
comment (#) nvidiafb, uncomment vesafb
write, save, exit
nano /etc/modules, add nvidiafb
write, save, exit
nano /etc/initramfs-tools/modules, add nvidiafb
write, save, exit
update-initramfs -u
nano /etc/X11/xorg.conf and add:
Section "Screen" Identifier "Default Screen" Monitor "Default Monitor" Device "Configured Video Device" DefaultDepth 16 EndSectionwrite, save, exit
nano /etc/yaboot.conf and add to the append lines to read "quiet splash video=offb:off nomodeset single"
write, save, exit
ybin -v
Type "passwd" and add a root password
Reboot
You should come to a screen that says "Enter root password for maintenance or Control D to continue"
Hit Control D and you should get the Ubuntu Mate desktop
Thanks again to Gary R.