Reason being, I am not using an RPi. I have an old laptop with Ubuntu and HA installed and have the USB RF Receiver plugged in to it.
Is this type of thing only possible with a Raspberry Pi?
The 433toMQTTto433 gateway works independently. You just need to plug in the power and it will connect to your WiFi. The RF signals it receive will be publish to an MQTT broker (server).
Anyway, you need to understand MQTT in order to use this. Once you get it (it is pretty easy), you can make use of it in your HA via MQTT. MQTT is pretty amazing for home automation. Learn it, you won’t regret it.