The latest firmware supports setting the user/PWD in the MQTT communication.

1 upgrade to the latest version https://imeter.club/topic/11

2 Set the user/PWD of the MQTT, follow the instruction in this way

https://www.iammeter.com/docs/integrate-with-mqtt-server#22--set-the-username-and-password-of-mqtt

Detailed Tutorial:https://www.iammeter.com/newsshow/mqtt-home-assistant-energy-meter-wifi

Video tutorial :https://www.youtube.com/watch?v=e8VYQqTReIo