I just switched from a Wii->HDMI adapter to a RGB SCART Cable -> HDMI Scaler.
I tested 576i on both the HDMI adapter & the SCART+Scaler setup. Both didn't work.
USB Loader GX (Games not loading in 576i)
Some games simply won't boot when I put the Wii in 576i mode. Forcing PAL50/60/480p...