My solution would be to have a sync-thinged folder, then, using filebrowser, create users for everyone you want to have access, and limit their access to that specific directory. Then your syncthing works like always, and the current directory is available online at anytime. It would be up to you whether to allow read/write/delete privileges on the firebrowser accounts. This way, whatever syncthing can’t work with, there’s still online access. Cloudflared access would be another good layer of protection.