Ubisoft has shut down online multiplayer services for 90 of its games, and player stats have been disabled.
For games using the Ubisoft Connect service, units and challenges will also be disabled, meaning you will no longer be able to earn units by completing the game’s challenges.
You can still unlock rewards in certain games, but you won’t be able to earn them in-game. If your games have not been transferred when Ubisoft migrates from Uplay to Ubisoft Connect in 2020, all rewards will be unlocked automatically.
The update released by Ubisoft also states that unlockable content like maps and skins will also be disabled, so you will no longer be able to unlock them.
On PC, unlockable content will no longer be available even if it has been redeemed before. On consoles it will continue to work unless you reset your saved game files.
Affected games include Assassin’s Creed 2, Beyond Good and Evil, Far Cry 2 PC, Far Cry Blood Dragon, Ghost Recon PC, Heroes of Might and Magic 5, Just Dance, Prince of Persia: The Forgotten Beach, Some older Rabbids and Rainbow Six games, Rayman 3 HD, Rayman Legends PC, and more.
Again, these are older games, many of which are already available on PS2, PS3, PSP, Wii, Wii U, and Xbox 360.
You can see the entire list of games at the link.