Examples: Broadcasting with a custom card

This is the custom card:

https://github.com/gadgetchnnel/lovelace-text-input-row

Create a broadcast script:

instant_message:
  sequence:
  - service: notify.alexa_media
    data_template:
       target: "{{ states('input_select.message_target') }}"
       data:
         type: announce
       message: "{{ states('input_text.message_text') }}"

Create an input_text where you can enter the text which has to be broadcasted:

input_text:
  message_text:
    name: Alexa message text
    initial: 'Enter your text here'

And make another input_select for the target:

input_select:  
  message_target:
    name: Alexa message target
    options:
      - "media_player.kitchen" # Echo device
      - "media_player.all_alexa_devices"  # Device group
    initial: "media_player.all_alexa_devices"
    icon: mdi:speaker-wireless

The lovelace code for the input row card:

entities:
  - entity: input_text.message_text
    name: Alexa message text
    type: 'custom:text-input-row'
  - entity: input_select.message_target
    name: Alexa message device
  - action_name: Send
    icon: 'mdi:voice'
    name: ' '
    service: script.instant_message
    type: call-service
type: entities

In this example I created a speaker group in Alexa called "All Alexa devices" and added all the speakers to it, which should be used when broadcasting. You can create different groups in Home Assistant too, which can also be used.