Can't check if state is unknown

Configuration
1

I’ve now tried several ways but I just can’t figure out how to check if entities are unknown. wind_chill is unknown but temperature is valid.

{{ states.sensor.gatineau_wind_chill }}
{{ states.sensor.gatineau_wind_chill is not defined }}
{{ states.sensor.gatineau_wind_chill is not none }}

{{ states.sensor.gatineau_temperature }}
{{ states.sensor.gatineau_temperature is not defined }}
{{ states.sensor.gatineau_temperature is not none }}

outputs

<template TemplateState(<state sensor.gatineau_wind_chill=unknown; state_class=measurement, location=Gatineau, station=Gatineau Airport, unit_of_measurement=°C, attribution=Data provided by Environment Canada, device_class=temperature, friendly_name=Gatineau Wind chill @ 2023-11-17T21:10:53.324788-05:00>)>
False
True

<template TemplateState(<state sensor.gatineau_temperature=0.8; state_class=measurement, location=Gatineau, station=Gatineau Airport, unit_of_measurement=°C, attribution=Data provided by Environment Canada, device_class=temperature, friendly_name=Gatineau Temperature @ 2023-11-17T21:10:53.320145-05:00>)>
False
True

2

unknown is simply a string value.

{{ is_state('sensor.gatineau_wind_chill', 'unknown') }}