https://www.pcgamesn.com/valve/pc-gamer-controller-use-triples
I'm glad this was mentioned here already. Big Picture mode in Steam is really something that I think might also contribute in increased popularity of controllers on PC. Back in the day it was really a struggle to get your already existing controller working on the PC (with Xbox it was easier after 360, PS needed extra stuff) but nowadays all one has to do is to pop into Big Picture mode and "it just works" given you've paired your controller with PC. This is with perspective over 15 years, I guess the support has been quite good multiple years already.