Because I spent so much time on this, doesn't mean we all have to. This python script configures a "doorbell" device in Home Assistant via MQTT.

This device has:

• A switch / toggle for the mute state. This also updates its own state;
• A button to ring your own doorbell "cuzz ya can";
• A trigger event as a "short button press" that you can use in automations;

  #!/usr/bin/env python
  # (c) 2022-04-24 S.E.Jansen.
  
  # Copyright (c) 2014 Adafruit Industries
  # Author: Tony DiCola
  
  #versie = "1.0"
  import time
  import paho.mqtt.client as paho
  import subprocess
  import MQTT_Config
  import GPIO_Config
  import json
  
  #call back function
  def on_connect(client, userdata, flags, rc):
      if rc==0:
          client.connected_flag=True #set flag
          print("connected OK")
      else:
          print("Bad connection Returned code=",rc)
          client.bad_connection_flag=True
  
  #Make connection with MQTT broker and
  paho.Client.connected_flag=False #Create flag in class
  paho.Client.bad_connection_flag=False #another flag
  
  client= paho.Client()                    #create client object
  client.username_pw_set(MQTT_Config.user,MQTT_Config.password)
  client.on_connect=on_connect #bind call back function
  print("Connecting to broker ",MQTT_Config.broker)
  client.connect(MQTT_Config.broker,MQTT_Config.port)	#establish connection
  client.loop_start() #start network loop
  
  while not client.connected_flag and not client.bad_connection_flag: #wait in loop
      print("In wait loop")
      time.sleep(1)
  if client.bad_connection_flag:
      client.loop_stop()    #Stop loop
      sys.exit()
  
  #the main loop starts here
  print("in Main Loop")
  
  print("Adding Doorbell " + GPIO_Config.ID + " action trigger")
  #Add doorbell button; as an action trigger
  topic = MQTT_Config.HA_name + "/device_automation/Doorbell_Button_" + GPIO_Config.ID + "/action_pressed"
  config_payload = {"automation_type":"trigger",
                    "payload": "visitor",
                    "value_template": "{{value_json.value}}",
                    "unique_id": "Doorbell_Button_" + GPIO_Config.ID,
                    "topic":topic + "/action",
                    "type":"action",
                    "subtype":"button_short_press",
                    "icon": "mdi:doorbell",
                    "device":
                        {"identifiers":[("Doorbell_" + GPIO_Config.ID)],
                         "name":("Doorbell_" + GPIO_Config.ID),
                         "manufacturer": "X",
                         "model": "001",
                         "suggested_area": GPIO_Config.location}}
  client.publish(topic + "/config",json.dumps(config_payload),0,True)
  
  time.sleep(1)
  
  print("Adding Doorbell_" + GPIO_Config.ID + " button")
  #Add doorbell; as output
  topic = MQTT_Config.HA_name + "/button/Doorbell_" + GPIO_Config.ID
  config_payload = {"name": GPIO_Config.location + " doorbell",
                 "unique_id": "Doorbell_" + GPIO_Config.ID + "_ring",
                 "name": "Doorbell_" + GPIO_Config.ID + "_ring",
                 "command_topic": topic + "/set",
                 "payload_press": "ring_short",
                 "icon": "mdi:alarm-bell",
                 "device":
                        {"identifiers":[("Doorbell_" + GPIO_Config.ID)],
                         "name":("Doorbell_" + GPIO_Config.ID),
                         "manufacturer": "X",
                         "model": "001",
                         "suggested_area": GPIO_Config.location}}
  client.publish(topic + "/config",json.dumps(config_payload),0,True)
  
  time.sleep(1)
  
  print("Adding Doorbell_" + GPIO_Config.ID + " mute switch")
  #Add doorbell; As switch. With state and command topic
  topic = MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID
  config_payload = {
                 "unique_id": GPIO_Config.location + " mute switch " + GPIO_Config.ID,
                 "name": GPIO_Config.location + " mute switch",
                 "state_topic": topic + "/state",
                 "command_topic": topic + "/set",
                 #"payload_on": "{\"mute_set\":\"ON\"}",
                 #"playload_off": "{\"mute_set\":\"OFF\"}",
                 "state_on": "1",
                 "state_off": "0",
                 "value_template": "{{value_json.mute_state}}",
                 "retain": True,
                 "icon": "mdi:alarm-bell",
                 "device":
                        {"identifiers":[("Doorbell_" + GPIO_Config.ID)],
                         "name":("Doorbell_" + GPIO_Config.ID),
                         "manufacturer": "X",
                         "model": "001",
                         "suggested_area": GPIO_Config.location}
                 }
  client.publish(topic + "/config",json.dumps(config_payload),0,True)
  
  time.sleep(1)
  
  client.loop_stop()	#stop connection loop
  client.disconnect()	#gracefully disconnect
  client.connected_flag=False #reset flag 

 I updated the python daemon accordingly. It has to listen to two topics and the action/trigger topic is also different.

Hope this is helpfull for someone. I spent almost a full day on the changes and it is still not perfect. I can't get the switch or the button to use the JSON payload. I really don't know where else I can put escapes or more single or double quotes. In the end I decided to skip the JSON for commands.

Also when the daemon encounters a non-JSON command on a subscribed topic, it crashes.. The code should use some proper exception handling, but I don't wanna.

#!/usr/bin/env python
# (c) 2022-04-24 S.E.Jansen.

#import lybraries
#import RPi.GPIO as GPIO
from gpiozero import Button as Button
from gpiozero import DigitalInputDevice as DigitalInputDevice
from gpiozero import DigitalOutputDevice as DigitalOutputDevice
import time
import GPIO_Config
import MQTT_Config
import json
import paho.mqtt.client as paho

#setup pins
button = Button(GPIO_Config.button, pull_up=False, bounce_time=0.05,hold_time = 3, hold_repeat=False)
bel = DigitalOutputDevice(GPIO_Config.bel)
mute_state = DigitalInputDevice(GPIO_Config.mute_state, pull_up=True, bounce_time=0.05)
mute_set = DigitalOutputDevice(GPIO_Config.mute_set)
mute_reset = DigitalOutputDevice(GPIO_Config.mute_reset)

#GPIO functions and callbacks
def visitor():
    #on rise of input (debounce 50ms) the doorbell has rung
    print("doorbel press detected")
    data = {'value':"visitor"}
    client.publish(MQTT_Config.HA_name + "/device_automation/Doorbell_Button_" + GPIO_Config.ID + "/action_pressed/action",json.dumps(data),0,False)
#MQTT connection + callback functions


def on_message(client, userdata, message):
    #check and handle incomming messages to:
	# - ring bell
	# - check mute status
	# - set bell to mute / unmute
    data = message.payload
    receive=data.decode("utf-8")
    #print(m_decode)
    #print (m_decode['Server_name'])
    if message.topic == MQTT_Config.HA_name + "/button/Doorbell_" + GPIO_Config.ID + "/set":
        #m_decode = json.loads(receive)
        #buttonpress = m_decode["doorbell"]
        buttonpress = receive
        print ("Button message received: "  + buttonpress)
        if buttonpress == "ring_short":
            bel.blink(on_time=0.1, n=1)

    if message.topic == MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/set":
        #muteCommand = m_decode["mute_set"]
        muteCommand = receive
        print ("Command received for mute: "  + muteCommand)
        #switch: for 
        if muteCommand == "ON":
            print("setting mute")
            mute_set.blink(on_time=0.5, n=1)
            time.sleep(0.1)
            data = {'mute_state':mute_state.value}
            client.publish(MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/state",json.dumps(data),0,True)
        elif muteCommand == "OFF":
            print("resetting mute")
            mute_reset.blink(on_time=0.5, n=1)
            time.sleep(0.1)
            data = {'mute_state':mute_state.value}
            client.publish(MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/state",json.dumps(data),0,True)
        elif muteCommand == "ENQ":
            #check status of relays. B-side is inverse of "mute" and is connected to GND. 
            #Pi is set with internal pull-up. Normal operation is mute off (bell rings normaly) 
            #A-side is closed, B-side is open.Therefore internall pul-up gives a value of 1.
            #value of mute is therefore inverse of pin-value.
            #mute = True means silent operation. mute = False means ring!
            data = {'mute_state':mute_state.value}
            client.publish(MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/state",json.dumps(data),0,True)
    
#def MQTT_AutodiscoverConfig():
    #send config to MQTT broker for autodiscover in Home Assistant
#    print("send Autoconfig message with MQTT")
#init

#Set callbacks:
#Doorbell button
button.when_pressed = visitor
#button.when_long_press?

#Mute change detect
#mute_state.when_changed?

#MQTT client
#client_on_message = MQTT_message
#client_on_connect .. etc
#call back function for MQTT connection
def on_connect(client, userdata, flags, rc):
    if rc==0:
        client.connected_flag=True #set flag
        print("connected OK")
        # MQTT subscribe to command topic to receive commands (in json format)
        client.subscribe(MQTT_Config.HA_name + "/button/Doorbell_" + GPIO_Config.ID + "/set",0)
        print("Subscribed to: " + MQTT_Config.HA_name + "/button/Doorbell_" + GPIO_Config.ID + "/set")
        client.subscribe(MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/set",0)
        print("Subscribed to: " + MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/set")
        data = {'mute_state':mute_state.value}
        client.publish(MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/state",json.dumps(data),0,True)
        print(json.dumps(data))
    else:
        print("Bad connection Returned code=",rc)
        client.bad_connection_flag=True

#call back function for disconnect MQTT connection to reconnect
#def on_disconnect

# MQTT details
paho.Client.connected_flag=False #Create flag in class
paho.Client.bad_connection_flag=False #another flag
client= paho.Client()                    #create client object
client.username_pw_set(MQTT_Config.user,MQTT_Config.password)
client.on_connect=on_connect #bind call back function
client.on_message= on_message                      #attach function to callback
client.connect(MQTT_Config.broker,MQTT_Config.port)	#establish connection
client.loop_start() #start network loop
while not client.connected_flag and not client.bad_connection_flag: #wait in loop
    time.sleep(0.1)
if client.bad_connection_flag:
    client.loop_stop()    #Stop loop
    sys.exit()

# MQTT Home Assistant autodiscover config

# MQTT subscribe to command topic to receive commands (in json format)
client.subscribe(MQTT_Config.HA_name + "/button/Doorbell_" + GPIO_Config.ID + "/set",0)
print("Subscribed to: " + MQTT_Config.HA_name + "/button/Doorbell_" + GPIO_Config.ID + "/set")
client.subscribe(MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/set",0)
print("Subscribed to: " + MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/set")
data = {'mute_state':mute_state.value}
client.publish(MQTT_Config.HA_name + "/switch/Doorbell_" + GPIO_Config.ID + "/state",json.dumps(data),0,True)
print(json.dumps(data))

#for silent testing..
#print("engage silent mode")
#mute_set.blink(on_time=0.5, n=1)
#time.sleep(0.1)
#print("mute status: ")
#print(mute_state.value)


while True:
    try:
#        print("still running")
        time.sleep(10)
    except KeyboardInterrupt:
        client.loop_stop()	#stop connection loop
        client.disconnect()	#gracefully disconnect
        client.connected_flag=False #reset flag
        mute_reset.blink(on_time=0.5, n=1)
        time.sleep(0.1)
        print("mute status: ")
        print(mute_state.value)
        print("returned doorbell to normal opperation")
        print("Ending program")
        exit()

And supporting config files:

#MQTT_config
broker="xxx.xxx.xxx.xxx"
port=1883
user="xx"
password="xx"
HA_name="homeassistant"

#Pins (GPIO numbering)
button=18
bel=23
mute_state=27
mute_set=24
mute_reset=25

#Unique sensor ID
ID="XX"
location="location"

Systemd services file:

[Unit]
Description=Managing doorbell with MQTT
After=network.target

[Service]
ExecStart=/home/user/python/GPIO_MQTT_daemon.py
WorkingDirectory=/home/user/python
StandardOutput=inherit
StandardError=inherit
Restart=on-failure
User=user

[Install]
WantedBy=multi-user.target

As always: use at your own risk :)