HomePod Software 13.4
You could probably be forgiven for missing the fact that there was also a software update for Apple’s smart speaker, but much like its other devices, HomePod software updates normally come along around the same time as the corresponding iOS updates.
There’s no real word on what this one fixes, other than the usually cryptic “general improvements for stability and quality,” and definitely no new features. The update should be installed automatically (another reason why you can easily forget about it), but if you’re an eager beaver who wants to put it on right away, you can do so with a quick trip into the settings in Apple’s Home app on your iPhone or iPad.
As an aside, it seems that Apple has gotten away from its earlier habit of referring to the HomePod updates as if they were some flavour of iOS (even though they undoubtedly still are under the hood). The label on this one simply says “HomePod Software Version 13.4.”