If reliable is seen as bombproof, easy to repair, and spare parts available in most parts of the world, I think it would be a pretty old school:
26” steel mountainbike, no suspension
V-brakes
Shimano components
7 or 8 speed triple drive
Platform pedals
Here’s mine, an old Miyata On Off Roadrunner, fully loaded for the pic, though I usually tour much lighter on a Bianchi Volpe
