I have a beagle so I would obviously say to get one.
Dont just get a dog to be a mtb dog. Consider all aspects.
Yeah, beagles are hard to train & are strong willed but they are really good with children/cats etc ( & chicks dig them )
We took our beagle everywhere with us, camping/walking/climbing etc from being young and he was perfect off the lead, so we thought 'beagles are easy to train'.
THEN 'dog puberty' starts, Finn was rubbish off the lead for a bit & we thought 'beagles are really hard to train'. But then we got him 'done' and he is now 2 yr old so he is now getting good off the lead again. (over the next few months we are going to be introducing him to some MTB trails)
Here he is wild camping at 4mts old (excuse my bed head)
And here he is more recently at the beach.
So its easy to say 'avoid like the plague' but you need to think about what you want, my beagle never causes any probs they are seen as a dog with very few health complaints, he is brill with ALL other dogs & is suprisingly good off the lead. (& pretty cute!)