This does narrow it down. I suspect powersave features are causing the issue.
Can you try booting and testing using the i915.enable_dc=0 grub parameter?
Following this guide:
Do Not Use nomodeset. Instead, use i915.enable_dc=0, so it looks like:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_dc=0"
Once the line is ready, tap ctl+o to overwrite, then enter key to save as current configuration.
Tap ctl+x to eXit the editor, then run:
sudo update-grub
Reboot, then test...