Update

I have created the Distro directory where I will upload the updated iso.

In this case I uploaded the version gabeos-live-installer-x86_64-5.8.18_1-20201116.

In it I changed the Display Manager Lightdm for GDM.

For those who have downloaded the iso above and want to use GDM, just do the following.

From the graphical environment, press the CTRL + ALT + F3 keys. This will open a tty.

Log in as a user and type:

sudo rm /var/service/lightdm

Then type:

sudo nano /etc/gdm/custom.conf

Place a # symbol in front of the following lines:

> AutomaticLoginEnable = true
> AutomaticLogin = anon

it should look like this:

#AutomaticLoginEnable = true
#AutomaticLogin = anon

Press CTRL + o and ENTER, to save the changes and CTRL + x to exit nano.

Then type:

sudo ln -s /etc/sv/gdm /var/service

Then restart the PC with:

sudo reboot

Cheers