In reply to cb294:
> ... She has permission to drill into the walls, but I would still need to find a board (or a separate mounting system) that will hold on a wall presumably made of straw, clay, and cow dung!
> ...I am currently in favour of super gluing a wooden board to the wall, onto which the actual board would then be mounted using conventional bolts.
Glue is not the answer, particularly not superglue. Even if the glue itself worked you would probably find that the sub-strata were only weakly bonded and you'd just end up pulling the board away with a chunk of wall attached.
Buy or borrow an electronic stud detector and screw a suitably-sized sheet of thick-ish ply through the wall into the beams, since you say you have permission to drill. Then fix your hangboard to that.