Apple has recently released iOS 15.4, which brings with it AirTag misuse alerts, Universal Control, and updates to Face ID to name a few added features.
Probably the most useful update of the bunch are the Face ID changes, which let you use Face ID with your mask on.

Additionally, Universal Control lets you use other Apple devices as secondary screens, and is available on the following devices:
- MacBook Pro (2016 and later)
- MacBook (2016 and later)
- MacBook Air (2018 and later)
- iMac (2017 and later)
- iMac (5K Retina 27-inch, late 2015)
- iMac Pro
- Mac Mini (2018 and later)
- Mac Pro (2019)
- iPad Pro
- iPad Air (third generation and later)
- iPad (sixth generation and later)
- iPad Mini (fifth generation and later)