Nvidia dGPU and slow performance on HDMI

[Swampebob]

I've connected an Asus 24 inch gaming monitor with 60Hz to HDMI on my HP Pavilion Gaming Laptop 15-dk0xxx.
It has an Intel GPU for the monitor and a dGPU with Nvidia GTX 1650.

I'm running DayZ completely fine on the internal monitor and have FPS on over 100. I launch it with this command from Steam to offload the graphics to the nVidia GPU: NV_PRIME_RENDER_OFFLOAD=1 GLX_VENDOR_LIBRARY_NAME=nvidia %command%
With the external monitor I get the expected 60 FPS, but it is extremely slow. Even when I log in to Gnome I experience intermittent freezing of the mouse pointer for fractions of a second, just like I experience in the game.

I've tried various solutions from this thread: https://askubuntu.com/questions/1244674 ... emely-slow

None of these solutions work. There is a couple solutions that is repeated in different forums. One is to select Nvidia Performance mode instead of Intel Power Saving Mode.
I know you can do this either from Nvidia settings or by running the prime-select command. These options aren't available on Debian.

Can someone lead me in the right direction on how I can fix this?

[@ttila]

I remember Nvidia drivers give a lot of issue when the user uses an external monitor, probably latest drivers fix the issue. Perhaps a solution is here.