hello, I had a problem with hidpi screen on linux (ubuntu mate, 20.04):

everything looks good using a 4K screen, everything is also ok when using only one 1920x1080 screen, but pd (and only pd) use very big font when using both screen in the same time. The solution was to set dpi with : "xrandr --dpi 80" in a terminal this fix pd resolution. I just send this information here since there are few mail about hidpi in this list with no answer.

hope it will help other cheers Cyrille