But all that said, I would love to hear what other recommendations folks might have for this kind of riding. I ride a lot of road, but bikepacking is a new frontier.
I'll give the same answer I always do. A steel single speed 29er is the true chameleon, one that you can add gears and a suspension fork to if desired. Salsa el mar, older Kona Unit, Karate Monkey etc...This State looks like it fits the bill to. You can put skinny tires on a mountain bike but you can't put fat tires on a cross/gravel bike. Tires are the biggest limiting factor for different terrain, not gears.