Hi,
I am using affinity photo on windows and occasionally use pen input. I would appreciate the option to only draw with the pen, not by accidentally touching the screen with a single finger (or by palm rejection not working at that particular moment, or by simply forgetting what happens when you use a finger while drawing with a pen).
If that option is enabled (maybe only when a brush is actually the current tool), a little button next to the pressure sensitivity button could enable/disable that behavior. And then, maybe finger input could automatically be something else, like moving and selecting objects.
Best