This is the setup I am using to publish events for my Brink Flair 300 heat recovery unit. I have a Raspberry Pi 3, with an RS485>USB, connected to the 2 & 3 pin of the X15 input of the HRU. The flow in Node-Red talks locally to the device via modbus, and then connects to an mqtt server that is used for further connection to Home Assistant, this appears to be the most robust solution.
I used this USB stick: Rpi RS485 USB, but I think any of them will work. You do not need to buy the super expensive 'digital adapter' and the app, and with this setup you also do not need the super expensive RF bridge and connectors (though will likely want some physical alternative to this setup to turn it on / off if needed).
It currently provides temperature, set fan speed, actual fan speed, binary sensors for max, medium