Pi-hole stopped working efter update to Bullseye

Yesterday I updated my Raspberry Pi to version 11 (Bullseye). The main usage for my Raspberry Pi is Pi-hole; a network-wide ad-blocker.

But that stopped working and could not be started because of the following error; "FTL failed to start due to failed to create listening socket for port 53: Address already in use".
With the command

sudo netstat -nltup | grep 'Proto\|:53 \|:67 \|:80 \|:471'

I figured out that a system component of Raspberry OS version 11 was bind to port 11; connmand.

Since that system component is optional, you can easily uninstall it with

sudo apt purge connman

After a reboot I was able to start my pi-hole again and could FTL (from Pi-hole) use port 53 again.