May want to hold off on playing until a fix is deployed.
Watch Dogs: Legion

Numerous players of Watch Dogs: Legion have reported a significant problem following the release of the game. They say that there is an issue with the game's save system in that is just seems to not work at times and at other times it outright corrupts whatever existing save is present. This has been reported both on the Watch Dogs subreddit and through the game's official forums.

The issue is compounded by the fact that there is only one save slot and no option to manually save. The issue ranges from players losing hours of progress to losing their entire campaign.

It appears as though one of the issues here is that saving on exit takes so long at times that some users are using ALT+F4 to close the game prematurely. This can lead to save corruption. The length that this closing process takes seems to vary from user to user, with some taking as "little" as five minutes while others saw that the game was still hung up after over half an hour later.

There is a workaround, one that was shared by a Reddit user. They say to disable the cloud service and start Ubisoft Connect (formerly Uplay) in offline mode. Then from there, you may need to set Watch Dogs: Legion affinity to a single core that isn't CPU 0. Then return to a game and quit out to the main menu. Supposedly this will allow you to quit after a brief pause.

Ubisoft seems to be aware of this save corruption issue but a fix is still "days" away.

"We’re aware some players are having difficulties and we’re looking to address these issues in an upcoming patch by November 9," a Ubisoft rep said in an email to PC Gamer. "We’ll have more information on the contents of the patch in the coming days."
The save corruption issue is just one of many issues plaguing Watch Dogs: Legion. Performance on the PC is abysmal across a large swath of hardware, even on the newly released RTX 3080 video cards. Even the game's DirectX 12 implementation seems to offer far worse performance across all CPUs despite the fact that it should offer better performance. Multiple users have also reported that the DLSS implementation is just flat out broken in the game.