Hi again marcocim,
Though currently HiveMQ Cloud free/pay as you go clients won’t use their own certificates for connection, if your device needs a root certificate for HiveMQ Cloud check our FAQ here (second item in the list):
https://community.hivemq.com/t/frequently-asked-questions/514
The certificate is in .pem format, but this can be converted with openssl to .crt or other formats as needed depending on the device.
To better understand what you are facing with the Minew G1, we looked around some and found this guide someone made for connecting to Amazon:
https://revolution11blog.com/2019/04/30/configuring-the-minew-g1-wi-fi-ble-gateway/
In the “Setting up the Gateway with certificates and MQTT Publishing” section it shows uploading files to the device using a USB stick. I can’t tell if it will allow you to use just the root certificate there (leaving the client certificates empty), and any client username/password you’ve set up (in our HiveMQ Cloud console) in another screen though.
You may need to experiment. Please let us know how it goes!
Seth - HiveMQ Support