Template Sensor that ignores stale sensors

I am looking to write a template sensor that will ignore sensors that have not updated in X amount of time. I have put a bunch of random peoples code together, so i am sure i messed something up. But, it is not currently working.

- sensor:
    - name: "Average Downstairs 433 Temperature"
      unique_id: '5e9cd8d7-9516-4dda-b43f-9ebf31ae24cb'
      device_class: temperature
      state_class: measurement 
      state: >
        {% set t = strptime(((now().timestamp() - 300) | timestamp_utc) ~ '+00:00', '%Y-%m-%d %H:%M:%S%z') %}
        {% set sensors = [states.sensor.acurite_dining_room_temp_433,
                          states.sensor.acurite_living_room_temp_433,
                          states.sensor.acurite_kitchen_temp_433,
                          states.sensor.acurite_spare_bedroom_temp_433,
                          states.sensor.acurite_spare_bathroom_temp_433,
                          states.sensor.acurite_computer_room_temp_433,
                          states.sensor.acurite_front_bathroom_temp_433,
                          states.sensor.acurite_entryway_temp_433,
                          states.sensor.acurite_pantry_temp_433]
                          | rejectattr('state', 'in', ['unavailable','unknown',''])
                          | rejectattr('last_changed', '<', t)
                          | list %}
        {% set qty = sensors | count %}
        {% set x = sensors | map(attribute='state') | list | string %}
        {% set total = x.replace("'","") | from_json | sum %}
        {{ 'unavailable' if qty == 0 else (total/qty) | round (1) }}
      unit_of_measurement: °F

Hi scuppasteve,

Is that something written by ChatGPT or did you find it somewhere?
Check the syntax there on template (jinja) if-elif-endif loops.

I got it from this thread - Detect when a sensor has not updated for x minutes - Configuration - Home Assistant Community (home-assistant.io)

Read the EDIT on that post and do suggestion.