For those who don't know about cantis:
https://www.sheldonbrown.com/canti-trad.html
and his additional page on canti "theory":
https://www.sheldonbrown.com/cantilever-geometry.html
Or, you can loosen 2 bolts (with only one allen key!) and align a hydro disc caliper so the rotor doesn't rub and be done with brake adjustment altogether and forever.