HDR displays stay in SDR through a fullscreen window
Fullscreening YouTube in Chromium on a Pro Display XDR flipped the panel to HDR, and the SDR image turned washed out. A change merged into quattro sets cm_auto_hdr to 0, so displays stay in SDR. There is no HDR for now.
The option had been running at its upstream default, which switches an HDR-capable monitor into HDR whenever a window goes fullscreen. With the setting, the Pro Display XDR stayed srgb through fullscreen.