You need a RS232-USB TTL adapter, ideally with FTDI chip for example something like that: https://allegro.pl/oferta/adapter-konwerter-usb-do-rs232-com-ftdi-db9-1-5m-7708396188
On the comfoair side you can use either the RJ45 plug, you need to connect cables like that:
rj45 pin 2 -> rs232 pin 3 - yellow
rj45 pin 3 -> rs232 pin 2 - white
rj45 pin 8 -> rs232 pin 5 - green
You can also plug the RS232 plug to the socket in the comfoair - mine has it and I use it this way.
You also have to disconnect the Ease (or whichever you have) controller as two devices can’t be connected to RS232 at the same time.