Nvidia hybrid 455 hdmi single display is slow


I have Dell G5 with Nvidia. The notebook has hardwired HDMI output to the Nvidia GPU. I was using the nvidia hybrid 440 drivers and just today I’ve upgraded to the video-hybrid-intel-nvidia-455xx-prime in order to be able to utilize the HDMI output. The external monitor connected to the HDMI is working fine in the Mirror and Join Diplay modes, however when I switch it to the single diplay mode which I want to use then the system response becomes very, very slow, like 2-3s lag when I start typing, or have to keep left-click down for couple seconds to be able to move a window, etc.

Has anyone seen this behavior? Any ideas how to fix this?

❯ mhwd --listinstalled
> Installed PCI configs:
              NAME               VERSION          FREEDRIVER           TYPE
       video-linux            2018.05.04                true            PCI
 video-modesetting            2020.01.13                true            PCI
video-hybrid-intel-nvidia-455xx-prime            2020.10.04               false            PCI

❯ inxi -G
    Graphics:  Device-1: Intel UHD Graphics 630 driver: i915 v: kernel 
           Device-2: NVIDIA TU106M [GeForce RTX 2060 Mobile] driver: nvidia v: 455.45.01 
           Device-3: Realtek Integrated_Webcam_HD type: USB driver: uvcvideo 
           Display: x11 server: X.org 1.20.10 driver: modesetting,nvidia unloaded: intel,nouveau 
           resolution: <xdpyinfo missing> 
           OpenGL: renderer: Mesa Intel UHD Graphics 630 (CFL GT2) v: 4.6 Mesa 20.2.3

This is a know issue, caused by limitations in the Xorg server. If you don’t want to switch to “full-NVIDIA” mode, one workaround is to mirror the screens and set the brightness of the internal panel to the lowest.

OK. Thanks. Hopefully they will fix it. For now, I’m going to “turn off” the internal display by
echo 0 | sudo tee /sys/class/backlight/intel_backlight/brightness