https://wccftech.com/homepod-mini-features-hidden-temperature-humidity-sensor/

In October 2020, Apple introduced the HomePod mini, the $99 smart speaker that came in at a much smaller size than the original HomePod but shipped with improved features like advanced acoustics and Siri improvements. However, one feature that was not discussed by Apple during its online presentation was a temperature and humidity sensor present in the HomePod mini. Unfortunately, the sensor cannot measure environmental metrics since it is disabled through software, but its presence in a $99 smart speaker may have some positive outcomes.

The hidden sensor was located by iFixit after an inquiry from Bloomberg, who discovered the hardware addition in the HomePod mini. Measuring 1.5 x 1.5mm, the temperature and humidity sensor is present at the bottom edge of the plastic case, where the braided power cable is present. It is made by Texas Instruments and is called the following.