@elupus First - thanks a lot for creating this integration.
I’ve not seen anyone commenting or writing about the serial modbus connection yet. I can confirm that my F1245 works using the serial:// URL and connected to the USB port on my RPi4. The connection is USB → RS485 dongle → Nibe MODBUS 40 shunt → F1245 heat pump.
One thing I would like to ask - the HA entities are currently logging/updating values only every 5 minutes. In between everything shows as “Unavailable” on the dashboard. Is there a way to set the update interval to a shorter period? I don’t see anything about this in the documentation and could not figure it out from a quick look in to the source code. Everything I read is in the LOG.SET file on the heat pump and I can read it in short intervals through my Python test script using @yozik04 's nibe library.