[Quoth]

The Kobo pen seems to be similar or identical to the MS Surface pen. I have two different 3rd party MS Surface pen models and button layout & battery & feel is identical. All take different tips.

The Kobo (Libra 2 (only sketch pad), Sage, Elipsa and Elipsa 2) seem to have a threshold set for pressure (quite low) so "ink" is either on or off.

The ones I've bought on Amazon keep becoming unavailable! Three Adrawpen in 2022 and one other make Feb 2023.

Try different software on the Laptop? Only some specialist sketching sw will show pressure. Try The Gimp as it can vary width, colour or density with pen pressure, if the pen and driver support it.
I've one Linux annotation package that annoyingly is pressure sensitive so that normal pressure is faint and you have to write hard (Wacom) for regular annotation. Mostly for annotation you want normal pressure and on/off ink.

Edit:
For Wacom (both kinds), Apple Pencil and MS Surface/Kobo Pen it isn't the screen that's pressure sensitive, though it may also be touch sensitive (IR, capacitive or resistive), but digitiser hardware that communicates with the pen. The pressure sensing is done in the pen and transmitted to the digitiser. In the case of Wacom the pen is also powered from the host, going back even to 1990s and serial port drawing panels. USB wacom simply used serial over USB. Earlier Wacom pens for laptops used internal serial or serial over USB interfaces. The digitiser is usually behind the screen.

I did once have a digitiser tablet with no graduated pressure (called Tabby). The tip literally was a small on/off microswitch. It was dreadful to use and the Kobo Pen doesn't act like that on a Kobo. Also the two models of MS Pen behave identically on the Elipsa, Sage and Libra 2 Sketch pad to the official Kobo Pen.


Currently about £25 on Amazon UK for 1024 level MS Surface 3rd party pens. I've two "bookmarked" just now in my not-books Wish list.