The additional photography for Zack Snyder's Justice League seems to have wrapped with Snyder having filmed new footage for his cut of the movie. Jared Leto will return as The Joker but will have a different look than his debut in David Ayer's Suicide Squad. Joe Manganiello likely joined filming and Amber Heard returnied to shoot new scenes as Mera, alongside Ben Affleck and Ray Fisher.
Another cast member of Justice League who shot additional pickups was Ezra Miller, but, due to him filming Fantastic Beast 3 in London, it was impossible for him to physically join the other DCEU actos on set, which meant that Zack Snyder and Warner Bros. had to get creative.
In an interview with Zack Snyder, Grace Randolph asks him about "a funny story" on how he got a pickup shot of Ezra Miller. Zack Snyder explains that because Ezra Miller was shooting for Fantastic Beasts 3 in London, Snyder could not travel there in person due to the ongoing pandemic, especially for something so small. To get around this issue, Snyder was able to direct Miller's pickup remotely through Zoom with the help of the crew of Fantastic Beasts 3.
Elaborating further, Snyder says that he sent the Fantastic Beast 3 crew drawings and diagrams of what he needed Miller to do for his pickup, which they followed. The crew also set up three monitors that Snyder could see on Zoom, which showed the set, Ezra Miller, and the camera.
The crew also had Snyder's feed playing through a table attached to a stand on set, which was enough for Snyder to direct Miller as needed.
This exchange can be found below in Grace Randolph's full interview with Zack Snyder at the 19:15 mark.
WHAT THIS MEANS
It seems that the week of shooting for Zack Snyder's Justice League has indeed come to an end. As for what scenes Snyder could have done, pickups for Ezra Miller could be minor but important. It could have been additional photography for Flash scenes in the speed force, as seen in the trailer, or even for scenes with Kiersey Clemons, who was originally intended to play Iris West.
Despite Snyder only shooting a week of additional photography and pickups with various actors, there's no real telling what particular scenes he shot, considering that he was able to shoot pickups for Ezra Millar while he was half-way across the world. It's possible that Snyder could have done something similar with other actors, like Gal Gadot, Ben Affleck, or possibly Henry Cavill if needed.