After iOS 15.3 and iPadOS 15.3, Apple offers the final version of macOS 12.2, watchOS 8.4, tvOS 15.3 and 15.3 for the HomePod.
These versions bring some new features for some devices. Of course, they come with bug fixes and stability improvements. Apple does not really provide details on all the new features. We advise you to look at the Release note of each system, to know more in detail the novelties.
For example, macOS 12.2 adds 120Hz support with Safari on 14″ and 16″ MacBook Pros with M1 Pro and M1 Max chips.
For upgrades, you just have to use the same usual paths and launch the updates for each system.
Feel free to share your discoveries in the comments section.