Check out Natsu-Mon: 21st Century Summer Kid. It’s not Deck verified, but it’s platinum on ProtonDB, so it should work. I played it on Linux (albeit not on Deck) with no issue.

You just get to be a kid in the summer in a small Japanese town. I grieved when it was over because I wouldn’t get to see all the friends I had made anymore or go fishing or hunt treasure or catch bugs…

So wholesome!