Hi
Thank you for your message.
Please note that Apple discontinued Inter-App Audio quite a while ago, which they’ve already replaced many years ago via supporting Audio Unit for iOS.
Alongside, Inter-App Audio comes with many limitations, which we’ve summarized in the following article: Limitations of Inter-App Audio
I’d strongly suggest to get in touch with the app vendors, to ask them about their plans to release Audio Unit versions of their apps.
Hope that helps!
Best wishes
& stay safe,
Lars