We've the tags surfing and snowboarding. Especially "snowboarding" implies that skateboarding should be definitely on-topic since it evolved from it.
The development of snowboarding was inspired by skateboarding, (...)
From Wikipedia
Skateboarding, however, doesn't really feel like it would "fit in", does it? You don't really do it in "the great outdoors" but in the streets and specific parks.
And what about longboarding then? I think things like "downhill" and "travel" would work just perfectly.
Longboards can be used for traveling long distances. (...) Any skateboard can be used for long distance journeys, however, decks designed specifically for long distance trips are typically lower to the ground than regular top mounted longboards. (...)
I think both topics are big topics and would probably attract new users.