Linux Mint

Problem description: Screen will turn black for an instant (around 50 ms?) and go back to normal, black screens will mostly (but not always) be accompanied by a horizontal gray strip. Blinking happens fairly often from desktop view, it happens a little less when loading basic websites like forums from Firefox, but it gets borderline unusable when displaying a video, I only tested this on reddit though.

I installed Linux Mint "Zara" 22.2 Cinnamon edition for a 2015 HP ProBook laptop (can't recall the specific model rn), it's set up for dual-booting along with Windows 10 in legacy MBR mode (no EFI). Since it's a laptop it has an integrated Intel HD Graphics (520?) GPU.

The problem's been present since I first booted up the live session from the USB, I thought after installing it would go away since maybe the live session is less stable or something.

Windows works perfectly fine in regards to this though, so I know it's not a hardware problem.

Across the forums, for people with similar issues (I haven't found one that describes mine exactly) the solution is usually "Find the line GRUB_CMDLINE_LINUX_DEFAULT='quiet splash' and change it to GRUB_CMDLINE_LINUX_DEFAULT='quiet splash intel_iommu=igfx_off i915.enable_dc=0 i915.enable_psr=0 intel_idle.max_cstate=2'."". I have tried with each of this parameters at least once, rebooting each and none of them completely solving the issue. my current setting is probably the one described there except that it may not include i915.enable_psr=0.

And yes, each time I modified the file through sudo nano /etc/default/grub, saved it, and sudo update-grub-ed, which never reported syntax errors so at least that should be fine.

My screen resolution is 1366x768, if that helps in any way.

UPDATE 1: I tested and rendering to external monitors work fine, I connected the device to a TV through HDMI and the blinking would only occur on the laptop monitor. This would maybe suggest it's a hardware issue, but that wouldn't explain why windows works fine, and messing around physically with the lid doesn't seem to increase/decrease the flickering. On the other hand, certain websites make the blinking/flickering occur more often if rendered, e.g. Godot Docs, and especially, Stack Overflow.

Info: My laptop is an HP ProBook 440 G4, integrated GPU Intel HD 520