I went from cloud to local smb shares to nextcloud to seafile. Really happy with the latter. Works, no bloat, versioning and some file sharing. The pro version is free with 3 or less usernames. I use the cli client to mount the libraries into folders and share that with smb + subst X: into the root directory on laptops for family. Borgbackup of that offsite for backup.

I've read good things about Seafile and have considered setting it up on my Homelab... though when I looked at the documentation, it too seemed quite large and I worried it wouldn't be the lightweight solution I'm looking for.

Seafile works pretty well. The iOS app is ass though. Everything else is rock solid.

You might like Peergos, which is E2EE as well. Disclosure (I work on it).

https://peergos.org

You can try it out easily here: https://peergos-demo.net

Our iOS app is still in the works still though.

Syncthing is great, but doesnt offer selective sync or virtual files if you need those features.

Owncloud infinite scale might be the best option for a full featured file sync setup, as thats all it does.

I think you could replace Nextcloud's syncing and file access use cases with Syncthing and Copyparty respectively. IMO the biggest downside is that Copyparty's UX is... somewhat obtuse. It's super fast and functional, though.

Pretty happy with Resilio Sync. I use it on Mac, and linux in a docker container.

rsync, ftp, and smb have all existed for decades and work very well on spotty, slow connections (maybe not smb) and are very, very small utilities.

Unison. Unfortunately it has no mobile apps, though.

Copyparty. Found that recently and absolutely love it.