homeassistant.yaml

# config.yaml
sensor:
  - platform: rest
    resource: http://DECENT-TABLET-IP:8888/api/status/details
    name: Decent Espresso Status
    scan_interval: 10 
    value_template: "1" # This is a workaround for a bug. It does not allow a value of more than 255 characters.
    json_attributes:
      - state
      - substate
      - espresso_count
      - head_temperature
      - profile

I just thought this isn't needed anymore. I will add it again to the file.
    json_attributes:
      - state
      - substate
      - espresso_count
      - head_temperature
      - profile

switch:
  - platform: rest
    name: "Decent Espresso"
    resource: http://DECENT-TABLET-IP:8888/api/status
    body_on: '{"active": "true"}'
    body_off: '{"active": "false"}'
    is_on_template: "{{ value_json.is_active }}"
    headers:
      Content-Type: application/json

# lovelace card configuration

card:
title: Decent Espresso
type: entities
show_header_toggle: true
header:
  image: 'https://de.decentespresso.com/img/de1plus_brushed_grey.jpg'
  type: picture
entities:
  - type: attribute
    entity: sensor.decent_espresso_status
    attribute: state
    name: State
    icon: none
  - type: attribute
    entity: sensor.decent_espresso_status
    attribute: substate
    name: Substate
    icon: none
  - type: attribute
    entity: sensor.decent_espresso_status
    attribute: head_temperature
    name: Group Temperature
    icon: 'mdi:temperature-celsius'
  - entity: switch.decent_espresso

  # example for an "useful" automation - this isn't needed
alias: Decent ready notification
description: ''
trigger:
  - platform: state
    entity_id: sensor.decent_espresso_status
    attribute: substate
    from: heating
    to: ready
condition: []
action:
  - service: notify.mobile_app_my_phone
    data:
      message: Decent is ready to use
mode: single