Migrating from legacy templates

It sounds to me like you are still trying to mix up the two configs.

the old way:

sensor:
  - platform: template
    binary_sensors:
      some_template_sensor:
        friendly_name: ......
        value_template: "{{the template}}"
      some_other_template_sensor:
        friendly_name: ......
        value_template: "{{ the other template }}"

the new way:

template:
  - binary_sensor:
      - name: some template sensor
        state: "{{ the template }}"
      - name: some other template sensor
        state: "{{ the other template }}"

notice in the new way there is no main “sensor:” entry at the top. It starts with “template:” instead.

and there is no longer the need for “platform:” since the template sensors are now in their own domain (template) instead of under the sensor domain.