There’s syncthing-fork that I hope will continue to be maintained (especially as they committed a guide on how to switch from the official app 2hrs ago). I’ve used it already before the depreciation of the official app and it’s working reliably.

It looks like Play Store releases are planned to be stopped, so it’s probably best to install it either directly from the GitHub releases (for this, Obtanium is also a great tool for finding and updating apps from lotta sources), or with F-Droid.

Sounds like a job for the Lego Island Guy