I use Resilio Sync. It's not free, but was just a one time payment, not a subscription. Works on macOS, Linux, Windows, and they have an iOS app, too.
Sharing with others is possible, but they have to have the app installed to access the files. Resilion Sync doesn't provide any server through which you can download the files, it's all P2P.
I couldn't figure out their licensing or payment model for a team, everything led back to subscriptions and was hideously complicated. We went back to Dropbox because it just worked, no matter how much cruft its taken on.
Sharing with others is possible, but they have to have the app installed to access the files. Resilion Sync doesn't provide any server through which you can download the files, it's all P2P.