Can I use MQTT without AWS/Azure?

According to this document for communication via MQTT hosting via Azure or AWS is required.

How is it possible to communicate with a self-hosted MQTT server?

I succesfully communicate with my own mqtt server by entering my mqqt server details in the MQTT Modbus Gateway

Hi @mrh1997

It is only designed for Azure or AWS; however, you can try to test if it will work , Use AWS IoT Custom and upload the required certificates and keys

Best Regards
Maynard C