Hi David,
I've noticed that when the device is first booted, the "uci show mosquitto" command only shows this option "mosquitto.mqtt=mqtt", and after enabling it on the WebUI, the other options appear and stay even after disabling.
So, you can use the third option i've suggested, using a text editor like nano or vi, on the /etc/config/mosquitto file, and inputing the config parameters, that you've copied from another device already configured.
About the password file, i've checked and it has to be saved at: /etc/vuci-uploads/cbid.mosquitto.mqtt.password_filepassword.txt, and the location and name of the file has to be set on the /etc/config/mosquitto file, mosquitto.mqtt.password_file='/etc/vuci-uploads/cbid.mosquitto.mqtt.password_filepassword.txt'.
Best regards.
Best regards