I have written a short blog post on how to connect your FläktWoods FTX ventilation system to Home Assistant using modbus. It describes how to connect the system and configure your Home Assistant instance to communicate to it using a modbus gateway.
Since FläktWoods is a swedish product the blog post is in swedish, but I think it could be helpful anyway because I have included the full configuration I’m using.
https://framkant.org/2022/10/kontrollera-flaktwoods-ftx-ventilation-med-home-assistant/