Comment by adolph
A differently complex and smaller approach might be to combine the knob with with an axial flux PCB-BLDC, like what Carl Bugeja made [0, 1]. It might be suited to get haptics in something as small as the article's knob, although to get an in-built display you'd have to use one of those displays that fit in lego bricks [2, 3] with a slip-ring.
0. https://microbots.io/products/motorcell
1. https://www.youtube.com/watch?v=CVszJMlvZcA
Many thanks for the links/references. I don't really care about the display itself (probably prefer without it actually), but never saw those other links before, interesting stuff.