Hello McMelloW,
You wrote:
A pitty Domoticz does not have a proper MQTT connection. Now you have study and configure Nod-Red.
I do not have the problems you obviously encounter.
Have you installed a hardware device under "Setup" => "Hardware", called MQTT Client Gateway with LAN interface?
If so, configure the IP address of the MQTT server, if that server (broker) is installed on a different piece of hardware.
If it is installed on the same hardware, use localhost.
Leave the port (1883) as default.
If you have not secured your MQTT server with a username/password leave those fields blank.
However, I recommend to do so, but for now you can leave it.
Leave the "Publish Topic" as default (out)
See the screenshot above.
For this moment your MQTT interface is configured.
Now it is time to configure Node Red with MQTT.
From the "Network" section (Node Red, version 1.0.3) drag and drop the node "mqtt in" to your work space.
Double click on the node and the following will appear:

- Screenshot_VoC_12.png (18.58 KiB) Viewed 19801 times
Feel free to give the "Server" a name, to your liking.
Configure "Topic" as domoticz/out.
QoS and Output, you can leave as default.
Feel free to give the node an "Name", e.g. Domoticz Out
Next click on the pencil, right of server, and the properties will appear:

- Screenshot_VoC_3.png (28.45 KiB) Viewed 19801 times
In the Tab "Connection", configure the IP Address of your MQTT server.
If Node Red and the MQTT server are installed on the same hardware, you can use localhost
Leave the port as default (1883)
The rest you can leave, as shown in the screenshot.
In the "Security" tab you can configure the username/password, if you have the MQTT server secured with it.
"Messages" you can leave untouched for the moment.
Do not forget to "Update"
This view is closed.
Click on "Done" and on "Deploy" in the main work space.
You should now see een green square, indicating "connected"
You have now configured your Node Red interface to your MQTT server Broker. You need to do this only once.
Every time you use a mqtt in or mqtt out, your interface is configured.
Now, if you connect a "debug" node ( from the common section) to it, you should see all the data published by Domoticz (default to domoticz/out)
You wrote:
At the moment I am struggling to get something visible from the json node and the debug node.
If above works for you, you can change the topic to what your iSpindel publishes to.
Then you should see the data in the debug pane.
Now you can add the "json" node from the "parser" section. Next move your "debug" node to the output of the "json" node.
You should see the JSON output, like the screenshot above.
Can you publish that output?
Regards