I'm using Illustrator 25.2.1 (latest version) with a Surface Studio 2 (latest firmware, latest Windows update as of April 3, 2021.) Using the Paintbrush tool, with either a fixed or pressure calligraphic brush, when I draw a path with my mouse, the path is drawn showing the correct/expected stroke color (such as yellow) as I draw. However when I use the Microsoft Pen to draw on the touchscreen, the stroke is drawn in black until I lift the pen -- at which time it changes to the expected stroke color (i.e. yellow.)
Of course I've restarted my computer, and I've tried every different setting I could think of, such as using GPU versus CPU for graphics, to no avail.