It was bound to happen. Zwift has started offering mountain bike courses in their catalog.
Tried it. It was fun. Had a lot of trouble with the steering. Not sure what it was - if the steering was too sensitive or not sensitive enough… or both. There may have been a little lag in the response to my inputs. I found myself overcorrecting quite a bit - going off to one side of the trail, turning to get back on course and finding myself suddenly going off trail to the other side, turning to correct and find myself going off trail to the opposite side. Climbing was easier as the bike was going slower. Downhill… and the route starts you off downhill… was tricky… but it was fun. I don’t know about the value in training. I was pedaling slower because I was distracted and had to because too much speed would take me off the trail.
Haven’t tried it yet myself. Gotta get a handlebar mount for the phone to do it. Also my bike does not steer easily in the riser I use.