Old school me would say triple with a 11-34 at the back XT (ideally an old M737 but the newer 9 speed would work) and Ultegra but these days I would say 2X11 possibly see if I can run an 11-46 at the back and maybe a 30-44 at the front and use Gevenalle Levers which allows me to run everything from the bars while still having regular brake levers and my downtube/bar end shifters just mounted to the front. I remember a couple years ago doing a gear comparison and the 2x11 combo was pretty darn close to my old 3x9 combo maybe loosing a little off the top end speed which is fine I am touring and I think I might have gained a little on the climbing side.
https://www.gevenalle.com/product/gx/ (The front derailleur doesn't matter as it is friction but you need MTB 11 in the rear)
https://bike.shimano.com/en-US/produ...D-R8000-B.html
or
https://bike.shimano.com/en-US/produ...D-RX810-F.html (which might work better with really compact set ups)
https://bike.shimano.com/en-EU/produ...M8000-SGS.html
For cranks White Industries allows pretty much any combination so they are a good choice 30mm spindle with plenty of great external BBs out there but if you wanted to go cheaper Shimano GRX is an option but it would be a 46-30 and that would want to use the GRX front derailleur for sure.