Need help to activate device on first Sunday only

Configuration
4

Paste the YAML (correctly formatted) for your complete automation that “starts every morning”.

The template you have posted should return true if it’s the first Sunday of the month, so something like this should be fine, firing at 06:00 every day but only getting to the action on the first Sunday:

trigger:
  - platform: time
    at: "06:00:00"
condition:
  - "{{ now().isoweekday() == 7 and now().day < 8 }}"
action:
  [YOUR ACTION HERE]