I have an app that allows users to select data directories for storing config files. This allows customers to sync their settings using an existing syncing solution. Whether they use Google Drive, Dropbox, iCloud, SyncThing, or even Git is up to them.

The huge advantage is that most people already have some kind of syncing solution set up, and they can just use that. This is especially important for corporate environments where IT has to evaluate what's allowed and what isn't.

It comes with some drawbacks. Your code needs to be resilient enough to deal with inconsistent syncs, you have to use file system observation, stuff might be delayed etc.

But on the plus side, it seems to work very reliably, I've not gotten any complaints yet, and if something does go wrong savvy users can just fix it themselves. It's just a bunch of JSON files on disk, after all.

Most sync tools offer a way to share folders with other users, so if you do it right you get multiplayer for free.