If you have one screen at 192 dpi, one at 96 dpi, double the resolution of the one at 96 dpi and scale down:

xrandr --dpi 192 --output eDP-1 --auto --output HDMI-1 --left-of e-DP1 --auto --scale 2

I don't have my laptop with me, so I am not 100% sure. You can also go the other way, but the result is more blurry.

Otherwise, as said in another post, apply tips from ArchLinux wiki. I have also put my experience here: https://vincent.bernat.ch/en/blog/2018-4k-hidpi-dual-screen-... (notably if you want something a bit dynamic with a laptop).