Ubuntu20.04 has some problem with Guest Session. You can create a guest account with the following procedures
---
1. Select "Administration->Users and Groups ->Add" , to create a new "guest" user:
Name: guest
Username: guest
2. Select the "guest" user and go to the "Advance Setting"
1. Under "Advanced" tab, deselect "Disable account" box
2. Click on "Change" Password, and select "Don't ask for password on login" box
3. Edit "/etc/lightdm/lightdm.conf " file to disable the guest session created by Ubuntu20.04 and add logout procedure for new guest account
allow-guest=false
session-cleanup-script=/home/labdoo/Public/guest_logout.sh
4. Create a /home/labdoo/Public/guest_logout.sh file as followed
#!/bin/bash
if [ $USER = "guest" ]
then
rm -r /home/guest/*
cd /home/guest
mkdir Desktop Documents Downloads Music Pictures Public Templates Videos
chown guest *
chgrp guest *
rm -rf /home/guest/.mozilla/firefox
fi
You can find more extense and precise information on how to create accounts and manage their permissions from the following Linux Users Tutorial