Hello! Welcome to the forums.
I’ve been doing a bit of testing/troubleshooting with both an R16 and R16-J board.
I never had problems with my original two R16 boards, but intermittent problems with my R16-J. I THINK the J might be the older variant, HOWEVER I wouldn’t put it down to the chipset having any differences.
The strange thing that improved it was physically pushing down on the CPI casing. This obviously wouldn’t do anything, unless there were dry solder SMD points which I doubt.
My guess is the older models might exhibit some resistance in the ribbon connector, and pushing down simply reseated it slightly. I recall for the old GBA IPS screen mod, people were having screen pixel tearing issues, resolved by replacing the ribbon cable.
Potentially with the on demand governor, the throttled frequency and voltage mean less current being put through to the display, which may cause more resistance? I’m just guessing here, and haven’t looked anything up.
I’m going to be messing around with making a kernel with just the performance governor, based on 5.9. That is once I have some time. But if you know how to do that yourself, give that a go. @Joao_Manoel I completely forgot to respond to you! I was going to respond as soon as I tried it. Ha good old work/life!
See if you still get the screen distortion when plugged in via HDMI. If you don’t, then there’s a fairly high chance the problem lies somewhere between the CPI board and the LCD display.