@Hoffschmidt, Roman | 101 Detmold Thanks for posting in our Q&A.
For this issue, I have done a lot of research. In Microsoft Defender for Endpoint official article, it says that malware detection test and phishing test on Android Enterprise with a work profile, only the work profile is supported.
https://learn.microsoft.com/en-us/microsoft-365/security/defender-endpoint/mtd?view=o365-worldwide#pilot-evaluation
And Peter also said that " When using MDE for Android on a device with a Work Profile (personally-owned or corporate-owned), it will only protect everything within the Work Profile." in his blog.
https://www.petervanderwoude.nl/post/getting-started-with-microsoft-defender-for-endpoint-for-android/
Note: Non-Microsoft link, just for the reference.
Hope it will help.
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