When trying to load an ambisonics file using this project: https://github.com/robertncoomber/NativeiOSAmbisonicPlayback/
I get "Unexpected Ambisonics format".
Interestingly, loading a 3rd order ambisonics file works fine:
let ambisonicLayoutTag = kAudioChannelLayoutTag_HOA_ACN_SN3D | 16
let AmbisonicLayout = AVAudioChannelLayout(layoutTag: ambisonicLayoutTag)
let StereoLayout = AVAudioChannelLayout(layoutTag: kAudioChannelLayoutTag_Stereo)
So it's purely related to the kAudioChannelLayoutTag_Ambisonic_B_Format