I had this problem on linux mate and linux xfce version 22.04: screen goes off during playing movies.
Problem resolved this way: boot linux in recovery mode, activate network and enter root terminal. Then uninstalled xorg, mate or xfce, uninstall also lightdm. Purge those packets too!
Install again xorg then ubuntu-desktop, choose gdm as display manager (or greeter or whatever is called), then install cinnamon and everything posible related to cinnamon.
On next start choose cinnamon session.
This is the only way that worked for me, and i tried many, many solutions found on the internet but this one worked very good!
