I recommend Syncthing Fork, btw, it has a few more features.

You can set up a versioning system, there’s like five different options but I don’t know what all the differences are. You can set up your own custom amount of versions and set how long they are kept.

I have mine set to check for file changes, but you have a whole host of options for when it triggers. You can set it to run at intervals or just when changes happen, or when you do it manually. It uses damn near no battery life to keep on in the background for me.

It even has a conflict resolution system that let’s you observe file timestamp conflicts and resolve them manually.