Need help with integration SUPLA by MQTT

I am trying to integrate my 26 devices (55 channels in total) to which I have uploaded SUPLA software in various ways (some time ago, but it’s a different long story).
I started an intermediary on the docker in the form of Supla-mqtt-client and now I’m trying to create appropriate entries in the configuration.yaml file to handle all channels from the SUPLA server.
Here is what I managed by trial and error to make it show the correct state and you can send commands.
Configuration example for light:

  • platform: mqtt
    name: ‘LED strip test’
    schema: template
    state_topic: ‘supla/channels/status/relay/13239’
    state_template: ‘{{ “on” if value_json.on else “off” }}’
    command_topic: ‘supla/channels/command/13239’
    command_on_template: ‘{ “idx”: 13239, “on”: true }’
    command_off_template: ‘{ “idx”: 13239, “on”: false }’
    qos: 1
    retain: true
    optimistic: false

Unfortunately, I do not know how to use the availability status from the given payload for this configuration:
{“Id”: 13239, “caption”: “LED strip”, “on”: 1, “online”: 1 }
the “online” tag have the values 1 or 0
I have tried availabilty_template but it is not accepted.

Unfortunately, supla-mqtt-client does not work like Tasmota, so you cannot follow it, because the availability and state of the channel are in one topic - there is no separate topic for availabilty.

Command and payload are described here:

Can someone help me?