Planning on picking up Immortals: Fenyx Rising? You'll be happy to know that no matter where you purchase the game, Switch included, it will feature cross-progression.
Cross-progression is a feature that allows you to carry your save data from one platform to the next. Linking your Ubisoft account to any other account will allow progression to be retained for most Ubisoft games. For our newest releases, all your game progression is saved within Ubisoft Connect, so you won't lose a step if you change consoles or switch to PC.
Ubisoft specifically lists Immortals: Fenyx Rising as supporting this feature, so you can play on Switch and then continue your experience on another platform if you'd like.
Ubisoft also says that all of their new games going forward will support cross-play as well, but there's no specific titles mentioned just yet.