Voice SDK added to a PUN2 project causes conflicts

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We have a PUN2 (2.18.1) project I'm trying to integrate Photon Voice (1.23) into. Unfortunately importing the SDK from the asset store causes a ton of compiler errors (missing namespaces, classes, using directives etc.). This is reproducible on an empty project.
Some of the issues seem to be from asmdef dependencies being all wrong, but there are also some name differences (PhotonNetwork.inRoom vs PhotonNetwork.InRoom etc).

My question is: is there a version of the Voice SDK that we can seamlessly drop into a PUN2 project?

sample errors:
Assets/Photon/PhotonRealtime/Code/Extensions.cs(40,19): error CS0246: The type or namespace name `PhotonView' could not be found. Are you missing an assembly reference?
Assets/Photon/PhotonRealtime/Code/LoadbalancingPeer.cs(691,133): error CS0246: The type or namespace name `EncryptionMode' could not be found. Are you missing `Photon.Realtime' using directive?

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