Wow, great answers! Appreciate all the input. @
icemilkcoffee I'll be likely using rim brakes (cantilever or V), so good to know about 11 speed hubs. Wheels are not my wheelhouse (/bad pun).
Used GRX parts are even tougher to find than 3x9 here - otherwise that was my first thought.
Shimano isn't much help on their website (FFS, why have a compatiblity chart and not link to the specs PDF on each item?
), which is why I rely on the collective minds of BF to help me out.
From what I remember, 10+ speed MTB RDs don't work with road shifters.
I think it's going to come down to brifter availability. 3x9 used brifters would be a miracle or I'll have pony up the cash for new microshifts. Bar ends are fine for touring, but as a commuter they can be somewhat cumbersome.