Comment 8 for bug 2008951

After much searching I decided to install "lightdm" display manager. I was able to accomplish this using the advanced options on the grub boot menu, and choose ubuntu recovery mode.

When the menu appears, choose to activate the "network", then choose to enter "root" shell. Then type:

apt update
apt install lightdm

Part way through the configuration it will ask to select the default display manager as it detects that gdm3 is also installed.

Choose "lightdm" as the default to startup. After the setup completes, enter "reboot" and continue as normal.

I am now able to get into my system, and it is now stable so far - 10 minutes into the session and no sudden shutdowns!