As for relegating the MTB for road, stop that 😛 . n+1 MTBs, ride one while the other needs a bit of TLC and swap. Hard tail or even singlespeed rigid for less complexity to need servicing often in cruddy conditions. Or just look after the bike, service & replace bits as necessary, don’t jetwash etc.
Creaking hubs though, I bet it’s still something else. Creaks as you pedal, or constant? When you go over bumps, standing or sitting? Creak or a squeal (brakes?) ?
Oh, and I’d look at the mech. From the rear end I usually find it’s the mech. Creaky spring, jockey wheels creaking, possibly even seized jockey bearings but it may still go round by acting like a bushing, but squeals at the same time.