I'm not a member of this project but I think it is fair to say that the Sync App is a little bit abandoned. The main program get fixes from time to time. I'm running PicApport for some years now so I would say it is very stable.
Regarding the Docker Project: There are some others around as well. There is not much needed in a container to run PicApport so I also build my own, which could be upgraded very easily by rebuilding the Container with the newest .tar file nearby.
You find it in a Gist here if you like: