https://www.techradar.com/news/some-nintendo-switch-games-wont-work-with-the-upcoming-cloud-save-feature

Nintendo is launching an online subscription service for the Switch later this month, which includes access to multiplayer capabilities, classic NES titles of years gone by, and cloud backups for game data – but apparently that last feature won't work on all your games.

Game Informer did some digging on the Nintendo website and found a "this game does not support Save Data Cloud backup" message on some titles, including Pokémon Let's Go, FIFA 19, Splatoon 2 and Dark Souls Remastered. Nintendo has since confirmed to Game Informer that cloud saves won't work across the board.