It is unclear how much of a role the Manhunter will have in the Snyder cut of Justice League, and whether or not Lennix will be shooting additional scenes for the film.
“Re: Justice League and the Snyder Cut…
From his plans for the DCEU that Snyder has shared over the years, Swanwick’s reveal as the Martian Manhunter was supposed to happen in the first part of the intended Justice League trilogy.
In the comics, the Manhunter is the last Martian who accidentally got teleported to Earth and became one of its champions.