I'm honestly surprised that it's been almost ten years since the DCEU started, and there's barely been a single mention of Green Lantern in that universe. (aside from one brief line from Steppenwolf in Zack Snyder's Justice League and a small flashback cameo in either version of JL)
I get that the Ryan Reynolds movie doing poorly likely played a part in that, but I started reading Geoff Johns' run on Green Lantern, and it seems like there'd be a lot of potential for a movie no matter which of the seven Earth-based sci-fi-related Green Lanterns you pick. (nothing against Alan Scott, the golden age Green Lantern, but he's not really connected to the rest of them)
Heck, you could probably pick any two of
those seven and get a solid superhero buddy cop movie out of it.
Hopefully this means that the DC movies have a more concrete plan going forward, rather than seemingly throwing anything at the wall and seeing what sticks. (a movie based around the Trench? The ravenous fish people from a scene in Aquaman? Really?!)