In a nutshell: If you've enjoyed Watch Dogs: Legion but are ready for something different, you might be happy that Ubisoft added a new mode zombie mode in the latest update. It a public alpha test on PC only for now. Once it enters beta testing, console gamers should get a chance to play.
Watch Dogs: Legion of the Dead puts one to four players in London with zombies filling the streets. The main goal is to steal resource packages from Albion and Clan Kelley and get to the extraction point. Successfully surviving and completing the supply run with the minimum number of packages earns players "Z-Creds" to buy weapons and gadgets for subsequent runs.
Players start with a random survivor and gadget. There is no exporting leveled operatives from the Campaign mode, which seems reasonable for maintaining balance in a PvE affair. Plus, Legion of the Dead is an entirely separate game. From a gameplay standpoint, the mechanics are the same as in the campaign mode (video below). It's the overall goals that make it different.
The main focus is getting the supplies and making it to the extraction point. Killing zombies is not a prerequisite. In fact, Ubisoft says that one tactic is to lure Zeds to the enemy. While they are busy fighting the horde, players can slip in, steal the supplies, then sneak away without getting into a firefight.
You can unlock the Legion of the Dead mode from the Ubisoft Connect app (or website). It's under "Free Games." However, it is only available for PC players for now. Ubisoft says that it wants to ensure that it can deploy fast updates while in alpha testing and can best do that with the PC version. It said it would bring it to consoles, Stadia, and Luna once it reaches the beta stage but does not have a timeline for when that will be.