@marqs Sorry I didn’t come back earlier. This the original RGB cable from the French SNES, I can’t tell and I’m not eager to crack open it.
I tried the original composite cable, well I tried both of them because the composite cable from the GameCube was there too and I couldn’t tell them apart.
I tried both AV2 modes and none have a stable sync. Both display “AV2: RGBS 313p 15.62kHz 49.92Hz” on the LCD.
But the way, I tried a luma as sync cable I bought on rgc.co.uk for my SNES but it doesn’t change anything. No luck either with the comp as sync cable I bought for my GC.