I use both Syncthing and Nextcloud (each for different things). Nextcloud is more akin to Dropbox, and works very well. Syncthing is peer-to-peer, so you don't

I use both Syncthing and Nextcloud (each for different things). Nextcloud is more akin to Dropbox, and works very well. Syncthing is peer-to-peer, so you don't get a web UI you can browse on your phone and selectively download data (it's "all or nothing" per directory), but I haven't had a single problem with it in years. It just works.