Find the account objectid:
get-azureaduser
get-azureaduser -search "first-name-here"
Find the device objectid:
get-azureaddevice
Get-AzureADDevice |findstr /i 1AFA4NF
get-azureaddevice -search DESKTOP-1AFA4NF
Find the current Registered Owner:
Get-AzureADDeviceRegisteredOwner -objectid e894f302-8e07-4d09-8d48-16c7b1b5bff9
Add a Registered Owner:
Add-AzureADDeviceRegisteredOwner -objectid e894f302-8e07-4d09-8d48-16c7b1b5bff9 -RefObjectId 75d663ff-1f74-4549-bf07-715543f6e160
Remove a Registered Owner:
remove-AzureADDeviceRegisteredOwner -objectid e894f302-8e07-4d09-8d48-16c7b1b5bff9 -RefObjectId 1c9fe9c2-1740-4d44-b2d4-380493d7a5a7