I struggled a bit to get a correct Pi-Hole switch in Home Assistant. I finally found something that worked. It is not completely what I wanted, but at least it is working AND I can explain to my wife how it works.

I used the command_line platform to create a switch that is based on the output of a couple of commands:

switch:
  - platform: command_line
    switches:
      pihole_switch:
        command_on: !secret pihole_command_on
        command_off: !secret pihole_command_off
        command_state: !secret pihole_command_state
        value_template: "{{ value_json.status == 'enabled' }}"

In secrets.yaml I entered:

pihole_command_on:  "curl -X GET 'http://[IP address]/admin/api.php?enable&auth=[token]'"

The reason I use secrets.yaml so I can push my current configuration to Github, so you can profit from it.