From Comicbook.com:
It looks like Warner Bros. is embracing DC Comics’ approach to the multiverse as a new report confirms that Ben Affleck will reprise his role as Batman for The Flash, joining Michael Keaton as the second actor to return as Bruce Wayne for the upcoming take on the timeline-altering comic event Flashpoint. The news comes ahead of DC Fandome, the Comic-Con replacement event taking place entirely online after mass gatherings were placed on hold due to the ongoing COVID-19 pandemic. This will make Affleck the third actor playing the role of Batman in live-action, alongside Keaton and after the debut of Robert Pattinson in The Batman.
The report of Affleck’s return was confirmed by Vanity Fair, and it makes for a surprising return for the actor who was last seen in the poorly received Justice League. But he’ll return for director Andy Muschietti’s first superhero film, as he tackles the big-screen solo debut for the Scarlet Speedster in The Flash.
