For the sharing use case described a nice option is WevDAV. macOS, Windows and many Linux file managers have support and for the read-only case it is basically

For the sharing use case described a nice option is WevDAV. macOS, Windows and many Linux file managers have support and for the read-only case it is basically an extra HTTP verb that provides a machine-readable directory listing. Of course this doesn't solve the consumer side that is described here.