After a system upgrade, I got this annoying screen flickering happening at random intervals. Initially I thought the issue was Gnome related, but after a bit of research it turned out to be caused by a power saving feature on my Intel graphic card.
The solution to it is to disable the feature through a kernel parameter. For doing so you need to edit a configuration file specific to the chosen boot loader. In my case it's systemd-boot, so the file was located in /boot/loader/entries/[SOMETHING].conf (in my case the filename was the timestamp of my system installation, but mileage may vary).
Open the file with your favourite editor
sudo nano /boot/loader/entries/[SOMETHING].conf
Add i915.enable_psr=0 at the end of the options line.
Reboot, and enjoy your epilepsy-free screen time again.