MQTT Broker via Home Assistant add-on

Hi
I have HA on PI3.
MQTT add-on is installed and started with no errors in the log.
When i go to Intergrations the MQTT plugin is discovered now when i click configure the error below occurs. Plugin has been removed reinstalled, rebooted etc…
Any ideas ?

mqtterror

Many thanks
Jman

Update:
I rolled the HA version back to 2023.4.0 and the issue is NOT there anymore.
So this looks like a bug in 2023.4.1
BTW this is a clean new install

Regards
Jman

Post an issue on github then please.