Some internet connectivity check endpoints I see in my home networks:

- http://detectportal.firefox.com

- http://ping.manjaro.org/check_network_status.txt

- http://connectivitycheck.gstatic.com/generate_204

- http://captive.apple.com

- http://www.msftconnecttest.com/connecttest.txt

- http://api.ipify.org

The manjaro one will respond with "NetworkManager is online" when accessed from curl, but redirect to manjaro homepage when accessed from a browser.