There are many forms of scentwork, so it would be easier for people to make recommendations if you have a specific type in mind. Nosework is a relatively new "sport" in which dogs use the same sort of search and scent discrimination behaviors that detection dogs use. Tracking varies depending on which venue you plan to track in, as IPO tracking IME focuses on "style" as well as ability to follow the track moreso than AKC tracking. Working (SAR) dogs may also use trailing and airscenting to follow humans, I don't know that there's a sport which tests ability for those behaviors (except for bloodhounds for the former). I'm not sure how common it is to crosstrain between the different forms of scentwork, and you might use a different trainer for one vs the others. I've done some tracking with both my current dogs, and do some play "nosework" stuff with Bus. Both dogs have enjoyed it, and it's something any dog can do due to the wide scale of physical exertion needed.