this bug still occurs on a new card (5090), new cable (DisplayPort 2.1), and a new monitor (LG 5K2K 45" OLED Gaming Monitor - 45GX950A-B | LG USA). If you toggle HDR within gamescope-session on a NVIDIA gpu, it corrupts your entire display with flickering artifacts:
nvidia-bug-report.log.gz (622.6 KB)
WARNING: FLASHING LIGHTS
That clip was recorded at my monitor’s native resolution of 5120x2160p after toggling HDR from off to on.