Learned something today. There is, in fact, a sensor under the lcd screen on the 2021 Model Y. I opened mine up to have a look and it is a fancier sensor than the old Model 3. It has a built in fan to draw in cabin air presumably. I can see it spinning. However, this sensor doesn’t appear to have any effect on the AC system. Warming it up made no difference. I even tried disconnecting it and the system still appeared to work the same and the reported cabin temperature on the app still updated as usual. So… while this may be a temperature sensor, it is not the one measuring cabin temp apparently. There must be another somewhere.
I wonder if this is a humidity sensor?