I've worn my various Garmin devices while playing tennis going back several years. Drills, matches, practices. It's great to keep track of places I've played, HR data, etc. I don't understand why tennis is not one of the activity types, especially when there are activity types like "wingsuit flying". I have to use "other" as the activity type. I would suggest a tennis category with, like I said, Drill, Practice, Match as activity type. Not sure if this forum is the best place to get a suggestion to the Garmin Connect team, but I thought I would give it a shot.
Mike