On some Nokia 8.1's the notch is hidden. But worse the settings for showing or hiding is also hidden. I found a post on the Nokia forum where it shows how you can open the settings with Automate. I don't have that app, but I do have Tasker. I could add a task that sends an Intent to open the settings. This is it:

Send Intent:
  Package: com.android.settings
  Class: com.android.settings.Settings$NotchSettingsActivity
  Type: Activity

Yesterday I received the parts for the opentherm gateway. It's a small board that lets me connect the heater and thermostat to my network. With this I should be able to control the heater and thermostat and read the temperature with Home Assistant.

Today I soldered the kit and flashed the NodeMCU that connects the board to the wifi network. It already works standalone and I can read the values through the network. Now I only need to connect the board with the heater and thermostat.