Starting in beta 3 (21A5284e) there is a note in the release notes about being able to prevent iCloud Private Relay using the Restriction payload with a boolean key of allowCloudPrivateRelay. The macOS device must be supervised.
ericholtam
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I supplied feedback (FB7776576) the other day on this and got a reply today saying this is working as expected. I've replied that is unacceptable as this is a breaking change with no viable workaround. Ideally, Screen Recording is made a per-user allowance instead of a per-system allowance and the user can enable per-app Screen Recording like they can Microphone and Camera access.
Please, please file feedback if you haven't already. Change can happen if enough noise is generated.