Even after numerous rewrites, director changes, and other identity-altering events since Warner Bros. started development on The Flash movie, it seems plausible that the film, due to hit in 2022, will take place in the timeline occupied by the Snyder Cut, rather than the theatrical release of Justice League. The evidence is thin, but it's there, and it's worth taking a quick look at, as we all try to figure out what the future of the DC multiverse is onscreen. The reason we think the movie could take place during the Snyder Cut timeline has to do with Cyborg, a character who has been rumored to be a major part of almost every version of The Flash.
In the just-released trailer for Zack Snyder's Justice League, Victor is seen screaming out in pain and terror as his father seemingly gives his own life to aid the League in part of its mission. Ray Fisher's character had a lot more screen time and a much more complex arc in Snyder's version of the film, and it seems as though that arc takes him all the way from being frustrated with his father at the start of the film to mourning him by its end.
During the brief panel in support of The Flash, producers hinted that Barry is the only member of the Justice League who, with all his family trauma, has the powers to do something about it. This likely suggests that the film will incorporate some of the ideas from Flashpoint, a story in which Barry Allen travels back in time and prevents his mother's murder, only to discover that doing so has compromised the integrity of the timestream and left the history of the universe badly damaged.
In the comics, Cyborg was one of the pre-eminent heroes of that timeline, in which there was no Superman.
Here's the thing, though; if you are going to go with the idea (and themes) of Flashpoint, it makes sense for Barry's on-screen bestie to be someone who has experienced a loss similar to Barry's, but who lacks the capacity to change it. It would essentially give Barry context for how lucky he is, and how he is misusing his powers -- and it could give some real angst to the relationship mid-movie, as Barry tries and fails to find a way to save both without ruining time.
Add to that the idea that the movie is going to introduce a multiverse to the big screen, and you have huge potential to play with which version of the movie they actually spin out of (in the theatrical cut, Silas Stone lives), and what the prime universe looks like by the end.
The Flash is expected in 2022. Zack Snyder's Justice League will be on HBO Max in 2021. A planned Cyborg movie is still, at this point, up in the air.