MQTT based sensors are not created?

[fribse]

Hey guys
I still have this package installed in my HA 2021.6.6
I can see that it was updated not so long ago, so I hope that it's still working.
I have two 'MQTT alarmpanel' by ThanksMister installed.
They, like the Wallpanel by ThanksMister, integrate to HA with MQTT.
Looking in MQTT with MQTT Explorer, I see this entry for one of the panels:

So for me that looks good.
But I don't see a battery entry created in HA.

I have the

configuration.yaml

mqtt: !include mqtt.yaml

mqtt.yaml:

  discovery: true
  discovery_prefix: homeassistant

What have I missed?