[Quoth]

With "The GIMP"
Go Edit -> Input Device (to see what there is and what it can do)
Select the Pencil or Brush
Then on the control panel that lets you select layer, pattern etc, find Mapping matrix and tick box for Opacity or Size (on side) and Pressure (1st across top).

If it doesn't work with The GIMP it doesn't have pressure exposed by the Windows Device Driver, but by default there might not be a mapping for pressure.

If there is no stylus input pressure under Input Devices, then the flaw is the device driver for the digitizer, not the pen.
Go Windows Device Manager and find the Digitiser and see what it's using. My experience with Win7 and Win 10 was that the Wacom didn't work and the external USB Sound Blaster didn't work because "Windows" automatically loaded the wrong drivers. Manually changing them in Device Manager worked.
I also had sound and SD card slot fail due to wrong drivers after an MS update to Win10 on a tablet. Only browsing to "Windows Old" (or something like that) and manually selecting the old driver worked.

GIMP is very configurable, so screen shots may or may not be helpful. Let me know.