Entity sensor.HOLIDAY (<class 'custom_components.calendarific.sensor.calendarific'>) implements device_state_attributes. Please report it to the custom component author.
I'm guessing this has to do with how in HA 2021.12.2 "device_state_attributes" has been deprecated and replaced with extra_state_attributes in 2021.12.0b1
Entity sensor.HOLIDAY (<class 'custom_components.calendarific.sensor.calendarific'>) implements device_state_attributes. Please report it to the custom component author.
I'm guessing this has to do with how in HA 2021.12.2 "device_state_attributes" has been deprecated and replaced with extra_state_attributes in 2021.12.0b1