@Matthew P , From your description, I know you want to see if there's any policy can make Azure AD joined shared multi-user device to be remote via RDP when in sleep mode. If there's any misunderstanding, feel free to let us know.
As intune support, I am not familiar with RDP. So i go to do some research and find that to RDP to a sleeping computer, we may try first waking the computer on LAN, then using Remote Desktop to access the sleeping computer. Here is an article list the detailed steps for the reference:
https://techthoughts.info/remotely-wake-computer-from-sleep-remote-connection/
Note: Non-microsoft link, just for the reference.
Based on the above article, I find some steps unable to configure via Intune policies. So maybe we can consider to set Sleep time out to 0 to make the device never sleep:
https://learn.microsoft.com/en-us/mem/intune/configuration/shared-user-device-settings-windows
In addition, to remote Azure AD joined device, there's some imitation and extra configuration needed, we can see more details in the following link:
https://learn.microsoft.com/en-us/windows/client-management/connect-to-remote-aadj-pc
Hope it can help.
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