@Lasse,Thanks for posting in Q&A.
From your description, I know you want to add unlisted AppStore app to Intune.
Based on my research, Microsoft Intune uses the Microsoft Store for Business and Education to manage and distribute apps to devices. If you have published your app on the Apple App Store, it may not be automatically available in Intune.
To make your app available in Intune, you need to submit it to the Microsoft Store for Business and Education.
You can follow the Microsoft 365 Store step-by-step submission guide to submit your app to the Microsoft Store for Business and Education. The guide provides detailed instructions on how to submit your app, including how to provide your listing information, decide on your availability date, and make sure you add your critical testing instructions.
https://learn.microsoft.com/en-us/azure/marketplace/add-in-submission-guide
Once you have submitted your app, it typically takes four to six weeks to complete the submission process and get it approved. On average, most apps require multiple submissions to pass the validation process, so make sure you follow the submission guide carefully to reduce the time it takes to get your app approved.
You can also use the Microsoft 365 app publishing checklist to determine if your app is ready to be published.
https://learn.microsoft.com/en-us/azure/marketplace/checklist
This checklist includes information on the metadata you need to provide, such as your app name, a short and long description of your app, icons, screenshots, and video demos.
Or you can refer the link below to Add an iOS/iPadOS line-of-business app to Microsoft Intune.
https://learn.microsoft.com/en-us/mem/intune/apps/lob-apps-ios
I hope above information can help you. If there is any confusion, please feel free to contact us.
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