By default NetworkManager waits for IPv4 dynamic addressing to complete but does not wait for the auto IPv6 dynamic addressing. To wait for IPv6 addressing to complete, either (1) change the network connection's IPv6 may-fail setting to no, and/or (2) change the IPv6 addressing method to manual or dhcp, to indicate that IPv6 connectivity is expected.
-t | --timeout seconds
-x | --exit
-q | --quiet
-s | --wait-for-startup
nm-online exits with status 0 if it succeeds, a value greater than 0 is returned if an error occurs.