Hi, I believe I found an error in the MQTT5 spec.
Apologies for posting it here, as I see no way of contacting on mqtt.org.

On page 35, lines 737-738:
Setting Clean Start to 0 and no Session Expiry Interval, is equivalent to setting CleanSession to 0 in the MQTT Specification Version 3.1.1.

But a bit up line 717-718: If the Session Expiry Interval is absent the value 0 is used. If it is set to 0, or is absent, the Session ends when the Network Connection is closed.

This is in contradiction with MQTT 3.1.1 as the session does not end, and lives forever? It must rather say:

• Setting Clean Start to 0 and Session Expiry Interval to 0xFFFFFFFF (UINT_MAX), is equivalent to setting CleanSession to 0 in the MQTT Specification Version 3.1.1.

Please correct me if wrong and misunderstanding this