Install iOS 12.4 for These Other Changes
iOS 12.4 brings support for HomePod in Japan and Taiwan so if you live in one of those countries and want to use HomePod, you'll want to download it.
If you skipped iOS 12.3, you'll get some smaller changes with iOS 12.4 that might be of some use to you. These features include:
If you skipped iOS 12.2, you'll get some additional changes with your iOS 12.4 update. These include:
Apple's improved the quality of the audio messages sent in the Messages app in iOS 12.2. The company switched to a new Opus codec at 24000 Hz.
With iOS 12.2/iOS 12.3/iOS 12.3.1/iOS 12.3.2/iOS 12.4 on board your device, .CAF files will also sound a lot better.