https://www.gamespot.com/articles/nintendo-says-mario-is-not-currently-a-plumber-app/1100-6453100/

Iconic Italian gaming character Mario is not in fact a plumber, at least not currently. While he might have worked on pipes and drainage solutions at one point in time, he has since moved on to focus more on "everything cool," according to Nintendo.

The newly updated Mario profile page on Nintendo's Japanese website says Mario is no longer doing professional plumbing work. The page explains Mario thusly (via Kotaku):