Hi,
this appears to be something similar to Microsoft NCSI (Network Connectivity Status Indicator),
which sometimes is described as “a false negative to try ruin your mood”.
The network-manager-config-connectivity-ubuntu package description is more specific:
"[…] contains a configuration file which enables Network Manager’s connectivity checking
functionality. Network Manager will try to connect to an Ubuntu server to determine the
connection status. This is particularly useful for captive portal detection.No user data is transmitted in the connectivity checks, but merely contacting the Ubuntu
connectivity check servers reveals that the user is running an Ubuntu(-based) operating
system with Network Manager."
First, such tests always leak your public IP address to the owner of that service.
Second, it does not seem to be useful in your scenario as you are most likely not behind
a captive portal. Since it is unclear what exactly makes NetworkManager think your
connection is bad, I would recommend to turn off this “feature”.
Thanks, and best regards,
Peter Müller