I had a Beagle growing up. My sister had a big mixed breed dog at the same time. I taught my sister's dog to walk, trot, canter, change leads, go over jumps. My Beagle taught me to leave her alone.
Since then, I've learned more about dogs and have had Chow mixes who have not always wanted to participate fully with me in my goals for their behavior. I have fostered 1 hound mix puppy (Coonhound) for a short while and what a sweetie pie he was! Derp! I still see him - his mix was GSD so that helps. His owners use a head harness, which I think must help a lot even though it looks awkward. You might want to see if there are any that might work. If not, the front hook type harnesses work nicely - but really the nose on the ground thing is only a problem if they won't walk with you while sniffing (to me).
But with the less into training, more into their thing, or their instinct thing, clickers work so well, NILIF, training classes that are FUN (hate ones that are not) but effective, and finding the things that your dog likes and rewarding them with it. Your dog might excel in something like nosework - but I would definitely be looking for something he can DO (agility, flyball, rally, etc.). Even if it is not competitive, just for fun - I don't compete but will do fun classes (trick classes too).
Are you near enough to Pat Miller's place? I would love to go there for classes!
He is adorable.
PS - one thing that is different with people who have some of the breeds or mixes, and people who only have GSDs, is the expectation that your dog is going to make jokes at your expense and outsmart you, but not be polite enough not to point it out like a GSD...so get ready to laugh!