Recently the screen of a Dell Latitude 7400 laptop I have (which is
running Devuan) started flickering.

I tried to deactivate/reactivate it (got a second monitor), unplug it to
let it run w/o charger, change the display's frequency... you name it.
I also tried to reboot on the previous 4.19.0-14 kernel, to no avail.

Could it be due to some update or it necessarily hardware fault-related?
What caught my eye is that the 1st time I tried rebooting it was doing
that on the GRUB screen. Since then, not anymore then.

Are there modules to look for/disable?
What else is there to try?
Bernard (Beer) Rosset
https://rosset.net/