Can you please follow these steps to enter the Recovery Menu:
Once there, arrow key to the bottom to Drop To Prompt.
Run
sudo nano /etc/gdm3/custom.conf
Arrown key down to the line AutomaticLoginEnable=true and place a hashtag in front to comment it out. It will look like:#AutomaticLoginEnable=true
Do the same for the line:
Automatic Login=$USER to make it #Automatic Login=$USER
Tap ctrl+x to exit the editor, then the y key to say yes to save, then the enter key to save current configuration.
Back out of the Recovery Menu and reboot or proceed to normal boot and test.