The Airthings integration for HomeAssistant doesn't provide the status of the LED-ring in my Airthings Wave Plus. It does fetch the data I need though, and is required for this template.
Luckily Airthings have shared their thresholds, making it trivial to read data from Entities and making a new Entity for the LED-ring.
The template is pretty self-explanatory. Edit name of entities to match your installation.
A custom card could be created for changing the color of the ring-icon, but I haven't bothered.