Raspberry Pi gateway setup

I am lost in the documentation.
Can Raspberry Pi be used as the gateway in Home Assistant?

I have this solution running using openhab, mqtt, mosquito and nrlf24 wired directly to RPi GPIO. I need to migrate from openhab to HomeAssistant but I’m struggling with the basic configuration.

I’ve done everything described here MySensors - Home Assistant

It is not working. What means the notice only the MQTT client gateway is supported?

Is needed to install mysensors again from the console plus configure/make as described here Building a Raspberry Pi Gateway | MySensors - Create your own Connected Home Experience? The mysensors integration in HomeAssistant needs to be there as well?