Seafile has a syncing client, and a drive client (Seadrive) for viewing files as if it was a shared drive.
Since moving to Seadrive I have not had a single support issue, nor heard of a single issue syncing, whereas I'd have them weekly with OneDrive to the point we'd have to delete their local files and re-setup OneDrive from scratch.
OneDrive truly is an abomination built on top of archaic Sharepoint.