Ubuntu 20.04 always forces me to create a new user at boot

I have newly installed Ubuntu 20.04, customized GDM3, installed my needed software and everything appeared to be successful. However, when I reboot, Ubuntu asks me to create a new user for some reason. I am unable to bypass this, and must create the user, after which I can log out normally. The login screen then shows both the new user and the correct original one, which I can log in to and continue.

I searched Ask Ubuntu and found 1 instance of a similar problem. Unfortunately the solution presented there (reinstall ubuntu-desktop) did not work for me.

The graphics driver is Nvidia 440.100, if that is relevant.

Can someone suggest a course of action to resolve this? I'm reluctant to re-install Ubuntu as there is considerable customization. Aside from this new-user issue, it's working perfectly so far.

[Edit] Oct.1/20 This issue was known in Ubuntu 18 and 19, and appears to be the same as [this bug][1].

I found that while researching for why, at boot, the syslog was showing these lines:

Oct  1 15:39:49 mynode tracker-miner-f[1871]:   (Sparql buffer) Error in task 0 (file:///run/gnome-initial-setup) of the array-update: There is not enough space on the file system for update operations
Oct  1 15:39:49 mynode tracker-miner-f[1871]: Could not execute sparql: There is not enough space on the file system for update operations
Oct  1 15:39:50 mynode tracker-miner-f[1871]:   (Sparql buffer) Error in task 0 (file:///run/gnome-initial-setup) of the array-update: There is not enough space on the file system for update operations
Oct  1 15:39:50 mynode tracker-miner-f[1871]: Could not execute sparql: There is not enough space on the file system for update operations
Oct  1 15:39:50 mynode tracker-miner-f[1871]:   (Sparql buffer) Error in task 0 (file:///run/gnome-initial-setup/gnome-initial-setup-uid) of the array-update: There is not enough space on the file system for update operations
Oct  1 15:39:50 mynode tracker-miner-f[1871]: Could not execute sparql: There is not enough space on the file system for update operations

The message is misleading, because the partition is only 20% used.

Solution 1:

While searching for why I was getting "not enough space", I stumbled on some suggestions for the 'force new user' issue:

1. Disable the gnome-initial-setup by commenting it out in /etc/xdg/autostart/gnome-initial-setup-first-login.desktop.
   The line to comment was:

   Exec=/usr/libexec/gnome-initial-setup --existing-user
   

   That seemed to fix the issue, but intermittently.

2. Remove gnome-initial-setup package entirely

    sudo apt remove gnome-initial-setup
   

3. switch from gnome login to lightdm

4. Finally, the one that worked:

    a) edit /etc/gdm3/custom.conf
    b) Add/modify: 
   
        [daemon]
        InitialSetupEnable=False