Comment 31 for bug 1722256

Is this related ?

"...a Connectivity Checking feature was introduced. Ubuntu 17.10 and onwards, you are presented with a question mark in network status whenever a Captive Portal is detected. This new feature works by pinging the http://connectivity-check.ubuntu.com URL, time to time, in order to detect a captive portal."
https://vitux.com/disable-connectivity-checking-on-ubuntu-for-public-wifi-captive-portals/