I have a laptop with a QHD (3840x2160) screen and an old external monitor 1680x1050.

I set DPI to 192 with
xrandr --dpi 192
and then scale output to my external monitor with
xrandr --output HDMI-1 --auto --scale 1.98x1.98
The issues I'm having, in order of priority:
1. my mouse on external monitor is locked/framed/restricted to top left quarter of the screen. My desktop stretches across entire external monitor, default plasma panel too, windows get drawn on all screen and when maximised occupy the entire screen, but mouse cursor won't move outside the imaginary quarter screen boundary.
2. mouse cursor often flickers when on laptop screen. Especially when moving, clicking or click dragging. It doesn't flicker on the external monitor.

Anyone got any tips on braking/eliminating the "quarter screen barrier"?