However, unlike Apple’s other flagship products, the HomePod doesn’t have a display to manage settings, instead, it offloads the work over to the iPhone. Not dissimilar to the Apple Watch.
The HomePod is currently available for pre-order and will be released on February 9th. At launch it won’t support stereo pairs or multi-room audio; however, the site notes that Apple appears to have hardcoded iOS 11.3 as the first version to support stereo pairing.
Since the HomePod is running a forked version of iOS, the version numbers are quite similar. When the HomePod launches, it will most likely be running its own version of iOS 11.2.5, which is the current version of iOS.
[Source]