Hopefully your shoulder is stable enough!

I don't know if its applicable, but I've done spin class with a sling (due to a minor rotator cuff injury) and found out that its still a pretty good workout. You do get a few odd looks in class.

Probably more related, an xbf had used his trainer during his recovery of a dislocated shoulder. No racing saddles (haha) and readjust your bike because you won't be able to lean forward.

Wishing you the best of luck to your healing and cycling addiction!