@zing Thanks! Did both those things, copied unicode.pf2 and added the insmod all_video line to my menu entry, worked only in combination with starting it in verbose, had tried insmod all_video yesterday quickly but it didn't work because of that.

On Pi5 the GPIO video signal isn't as clean as the Pi4. I've done extensive testing with a full list of details further below. The noise pattern is super slight, but it's more visible in games with solid colors, blue skies and white screens. It looks like striped or S-shaped waves that move across the whole screen sporadically with a subtle flicker. It requires a clean noise-free CRT TV and very good vision to spot, but if your eyes are sensitive enough you can't unsee it either.

The Pi5 is the only variable, there's no wavy noise at all with a Pi4.
Two Pi5's tested, multiple PSU's, two different GPIO hats. Exact same cables etc.

A game like Super Mario Bros. on NES is a good one to easily see the noise, but you can also just see the noise in the default recalbox os theme (Recalbox 9.2.2-pulsar - Raspberry Pi 5). It's not just recalbox, but other Pi5 adapted images show the exact same interference issue. The issue is a hardware one particular to the Pi5 itself.

Does the Recalbox Dual have this issue as well? Would love for more people with good eyes to try this out and confirm it there as well. But it feels like not a lot of people would be pedantic enough to notice this type of subtle interference pattern.

Testing details: Two brand new Pi5 4GB's tested, three different PSUs
tested including a new official Pi5 PSU which arrived today, two RGB Scart GPIO hats tested (Pi2Scart with a thick shielded Scart lead and the RGBPi one),
reflashed the SD card, no overclock set or anything in the config.
Same Scandisk 32GB SD card used and swapped between the
Pi4+5's, same PSU and both Scart hats tested on the Pi4 resulting in
perfectly clean video there, with the same cables in either of the Pi5's.

It's the same amount of slight wavy video noise from the Pi2Scart as
the RGBPi cable on the Pi5, also tested with and without the aluminium
case+fan. With and without a controller plugged in, no USB drive, no audio DAC
or anything either, directly plugged into the RGB Scart input of the
same CRT TV.

As good as the Pi5 is, the video noise is driving me crazy as I can't stop noticing it.

Thanks!

@zing Thanks! Did both those things, copied unicode.pf2 and added the insmod all_video line to my menu entry, worked only in combination with starting it in verbose, had tried insmod all_video yesterday quickly but it didn't work because of that.

@zing Just gave the beta a try, the USB drive I'm using is the same as I used when I was running Lakka.
What happens is that after giving me the blue window asking me how to boot recalbox it gives me "error: no suitable video mode found" "booting into blind mode"

After that point the screen flashes white once before staying black.

As for what I tested I tried editing the config with hdmi mode 16, just to test ( and some others I can't recall sorry ). 1920x1200 is the native resolution of the display, there's 3GB of ram installed in case that would matter.

Thanks!

Lakka works perfectly but I much rather use Recalbox, however this issue is driving me crazy, edited the config numerous times but no luck, and basically found nothing regarding recalbox about this issue in my search results.

The iMac is a 24" one from around 2007 turned it into an arcade machine https://i.imgur.com/vHBSOxm.jpg so really hope there's a solution, super appreciated!