@Håvar Eidslott,Thanks for posting in Q&A.
From your description, I know you are looking for a policy to turn off Copilot on iOS devices.
Based on my research, we can create an app configuration policy to turn off Copilot.
Here are the steps you can refer.
1.Go to Intune portal > Click Apps > Click App configuration policies > Click Add, then select managed devices.
2.In the basics page, select iOS/iPadOS as Platform and Edge as Targeted app > In the Settings page, select Use configuration designer as Configuration settings format > Enter com.microsoft.intune.mam.managedbrowser.Chat under Configuration key and false under Configuration value.
3.Then you can deploy it and it will disable Copilot on Edge.
Hope above information can help you, if there is any update, feel free to let me know.
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