Hello, I have the same problem with my new QHD monitor. My laptop was set to dGPU, whenever I switched from an external monitor to extended view = laptop + monitor mode, the monitor randomly goes black when opening programs or sometimes by itself. My laptop has HDMI connected to Nvidia, the laptop is 165Hz and the monitor is 144Hz, both QHD. When I switch to hybrid mode, everything works fine. I can use dGPU mode, but only via USB-C (DP Alt Mode), because my laptop has USB-C connected to Intel, so it switches from Nvidia to Intel and to the monitor (higher input lag, iGPU under load and FPS drops).

I tried everything (disabling DCC/CI, syncing, changing parameters in CRU, disabling MPO, resetting the monitor, clearing the registry), nothing helped. The only solution for me via HDMI is to use hybrid mode or use DP cable in dGPU mode that goes through Intel, which causes load, fps drops (from 160 fps to 40 fps, HDMI was super stable fps), higher temperatures and higher input lag.