Was the 4.1 MQTT broker removed from the updates?
I just spun up a VM install HassIo (supervisor Version 150, System: HassOS 2.11) to test some things with Ver. 4.1 MQTT. However I see no Ver. 4.1 from that system. Only Ver. 4 is available.
I have the 4.1 MQTT broker installed on my production system. Its working ok.
wierd.