@Peder21jensen Thanks for posting in our Q&A.
To clarify this issue, did you correctly set the role assignments? Please refer to the following article:
I have done the test in my lab. I add a user group in "Members" and add a device group in "Scope(Groups)". When I use the user included in the target user group to login in the intune portal, the device included in the device group will be listed in the portal. And I delete the device successfully.
Hope it will help.
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