Digital&analog to digital transfer

In my first projects I bought extra sensors to measure my environment. So I have a good basic knowledge of accessories. As far as the initial situation is concerned, the question now arises as to how I can, for example, transfer already collected measurement data into the digital world.
The example with my heating system: you can see 3 sensors with your snapshots.

Above the already digital display of the temperature, middle also a 7-segment display with the option of an RJ45 connection and below an analog barometer.

Do you see the possibility to make the data available (I found the optocoupler in my research) or am I forced to access a proprietary interface of the manufacturer (Brötje Heating) via RJ45?