Oh No! This is terrible news. This IMHO is one of the most irreplaceable projects out there. I don’t know of another cross-platform local file syncing app that comes anywhere close to this. I hope that it can continue even if it’s not through the Play Store.
Google seems to be torpedoing open source developments with a number of decisions lately. Maybe they see F-Droid as a threat now that EU is making them open competition? Maybe they just don’t care.
It’s a very stable, reliable, local, cross-platform file syncing that is pretty easy to set up. Basically, it allows you to have a shared folder (or folders) on multiple devices without using Google Drive, OneDrive, iCloud, etc.