The first step to fixing the “could not connect to host localhost: connection refused” error on Debian 11 is to make sure your network settings are configured correctly. Check that your network interface is properly set up and that your IP address is correct. If everything looks good, then you can try restarting the networking service. To do this, open a terminal window and type in the command “sudo service networking restart”. This will restart the networking service and hopefully fix the issue.
If that doesn’t work, then you may need to check for any firewall rules that could be blocking access to localhost. Check for any rules in iptables or ufw that might be blocking access from localhost. If you find any, delete them and try again.
Finally, if all else fails, you can try reinstalling the Network Manager package with the command “sudo apt-get install –reinstall network-manager”.