I am using
Windows 10 Education, Build 10.0.19041
Affinity Designer 1.9.0
Lenovo Thinkpad X1 Tablet Gen 3
The pressure sensitivity of the Lenovo stylus has been verified with other apps (specifically, with "InkPaint"). So the problem has to be related to the Settings of my Affinity products.
I have been unable to get any kind of pressure sensitivity to work, either with the "pressure" mode, nor with the "velocity" mode. (The problems with the "velocity" mode are also confirmed on a Windows desktop PC, with the same version of Affinity Designer).
This is NOT a problem with a Wacom tablet.
I have also NOT been able to establish any velocity-sensitive stroke/brush dependence on my "Affinity Photo 1.9.0"