I tried this a while back, when going 6700 XT HDMI 2.1 to LG Oled C2 HDMI 2.1 with proper cable i could not get RGB 444 with 'correct' colordepth in Bazzite (or any distro) Windows 10 or 11 does not have this problem. Apparently it's an issue with the HDMI board and proprietary drivers for linux.