[Google Pixel 3 Questions & Answers] jurugi:
Had the screen issue on a Pixel3, fixed it. I flashed Android11 official one by choice and didn't have to do major changes to fix the issue. I didn't have to reverse engineer anything. (If this is not the main thread for this issue with the OLED screens, sry, couldn't find the large one.)

I first noticed this white or greenish artifacts on bottom 2/3 of the phone after the first day setup of phone, when browsing Youtube the first time at night. Of course once it started, it seemed to not stop for a while, making me worry the new phone is already broken. There's a lot of pages of spam and speculation, to me I think the final conclusion is that it's either: overvolted/overclocked CPU, and/or not making usage of the GPU by default sometimes, causing heat and voltage issues. This is why it will work, but then upon using it a bit, it will start to flicker, basic heat mechanics.

It seems as people have goen pages talking about this issue across multiple phones that use OLED, it does seem to be a 'hardware' issue that can be mitigated or effected by a few settings such as AOD (always on display) or the setting "Always show time and info (increased battery usage)". However this is only a useful preference, nothing more, it might have like 1% impact on the screen/cpu usage.

Brightness fix:

You might also notice you can set brightness to higher amounts and it 'resets' the screen again.

Turn the phone off and wait for it to cool down (this can take an hour, or more, and falls in line with what every person who has it has said, that they just stopped, put it away, etc. and it 'fixed itself', etc.). You'll generally notice if holding the back of phone, it will generally be hot when this thing happens, this shows it's a heat dissipation issue; likely because of 2 issues: in my opinion this is a powerful CPU for the time that still is similar to the Pixel6's CPU (and they do tech suppression anyway, that CPU has more space and only about 350mhz more, after 5 years?).

The best fix to try is that phone needs to be locked (set oem locked, bootloader locked, after flashing), and check/set that the GPU is being enabled and used to offload tasks. This ensures to check the CPU is not in any compatibility mode and rendering all the graphics (which is technically, not designed to do). It does seem that the phone works well, if the CPU is properly offloading tasks to the GPU. This should be similar ofr any "OLed" type of issue, in this case I happened to fix the Pixel3.

This won't fix stuck pixels/ghosting, but will hopefully fix the OLED flickering (after heavy/medium usage):

In the official firmware you can try these fixes (in order of importance to preferences):

- if unlockable, lock the bootloader, set oem unlocked to 'off' (lock it again); one small ignored post on the internet as well as official android sources suggest: CPU processes the graphics in a compatibility mode sometimes when reading value for oem/bootloader unlocked, and it will thus try to software render the graphics, instead of offload to the GPU, causing overheating and screen tearing.

- let the heavy duty stuff (updates, initial install) just run for an hour (or few hours), such as get all your app updates on wifi, run setups, and phone might start getting hot; if it happens then wait until its cooled (or use brightness trick), you can leave screen off while it does mostof this

- once you can view the phone: unlock developer options if not already done

- set "System->Advanced->Developer Options->Stay awake" off

- set "System->Advanced->Developer Options->OEM unlocked" off

- optional, highly recommended: set "System->Advanced->Developer Options->Automatic Updates" off (use Android10/11 for this phone, don't receive their end-of-life updates and potentially phone breaking updates)

- set "System->Advanced->Developer Options->Networking->Tethering hardware accel" on

- set "System->Advanced->Developer Options->Hardware Accel Rendering->Override force-dark" on

- set "System->Advanced->Developer Options->Hardware Accel Rendering->Disable HW overlays" on

+ toggle some options so that you are sure the OS has set them right, and they are on/off as needed:

under "System->Advanced->Developer Options": "->Hardware Accel Rendering" & "->Drawing"

-toggle on/off Show view updates, Show hardware layers updates, Debug GPU overdraw, Show surface updates, Show layout bounds, Display cutout: change to anything then back to Default.

- under "System->Advanced->Developer Options->Monitoring->Strict mode enabled" toggle on/off

- tap "System->Advanced->Developer Options->Debugging->Feature Flags", it was blank for me

- tap "System->Advanced->Developer Options->Debugging->Graphics Driver Preferences", toggle off/on, and check every such app is Default (just making sure these are available for the GPU to use)

- set "Display->Adaptive Brightness" off (this actually changes 'brightness' a bit without always physically showing the bar move, so if using brightness trick, it will randomly cause the artifacts to actually happen by adjusting brightness down/up anyway)

- set "Display->Advanced->Lock screen->Always show time and info (increased battery usage)" off

- set "Display->Advanced->Lock screen->Lift to check phone" off

- set "Display->Dark Theme" on (allegedly better for the screen, but I just preferred it)

now wait or leave phone off for a while to cool off.

For me this fixed the issue: and I think the CPU while in unlocked mode was trying to run everything for some reason, and just ensuring the settings were set: only like 1 or 2 were direct changes.

- optional: if its official or locked, trying factory reset could work to rule out software issues, but likely won't fix the screen flickering issue, especially if you can go into bootloader, and the screen still flickers.

- Wait for it to cool down (1 hour), and then see if the changes took effect.

If the problem persists, I would just wait again a day or so, then try unofficial firmware(such as lineageos):

you can mess with the clocks, possibly even analyse sensors, and see what's going on. It should be making use of the GPU and offloading tasks to it, even when doing like hw-acceleration, watching a youtube video, etc. Again be sure to lock the bootloader properly after flashing. You should be able to underclock/volt down the CPU/GPU very slightly if it still does the issue and then it will simply go away. This is an issue even sometimes with bad clocks released on hardware, where downclocking can be useful to stabilize or reduce heat, and it hardly effects anything performance-wise.

anyway let me know if it helps, yet as I see, the suggestions itself are years overdue/late even if not;

if so then enjoy your 100$ version of the 1000$ Pixel6 that just doesn't have far camera zooming and is already the 1000$ slim/normal proportions, it is a pretty good phone.