I don't recall it ever being a dead project. They did have a time period where you had to either join the beta on Play Store, obtain the beta on Github releases, or use F-Droid and install the beta. They were working on integrating certain things and rewrites before doing an official release.

It was a pinned issue in their issue tracker.

The whole 5.7xx series were betas, and 5.800 started the official releases again