Microsoft has apparently discontinued support of RemoteFX in Remote Desktop Services starting with Windows Server 2019, Build 1803 and later.  Here’s the article:

https://docs.microsoft.com/en-us/windows-server/get-started/windows-server-1803-removed-features

That would be fine if there were an acceptable alternative available.  The problem is that there isn’t.  What Microsoft is calling an alternative: Discrete Device Assignment, has serious, show-stopper limitations that remove all high-availability features, live migrate, etc: https://docs.microsoft.com/en-us/windows-server/virtualization/hyper-v/plan/plan-for-deploying-devices-using-discrete-device-assignment

From that article:

Virtual Machine Limitations

Due to the nature of how Discrete Device Assignment is implemented, some features of a virtual machine are restricted while a device is attached. The following features are not available:

• VM Save/Restore
• Live migration of a VM
• The use of dynamic memory
• Adding the VM to a high availability (HA) cluster

PowerShell commands also depreciated

Further to this, starting with Build 1809 Microsoft also appears to have closed the back-door work around of using PowerShell commands to install the RemoteFX drivers.  Commands such as “Get-VMRemoteFXPhysicalVideoAdapter” no longer return any data.

NVidia Confirms

This NVidia article confirms (via a Footnote) that RemoteFX vGPU has been deprecated by Microsoft since Windows Server, version 1803.

https://docs.nvidia.com/grid/10.0/product-support-matrix/index.html

Bottom Line: RemoteFX is Gone, There is no Replacement for High-Availability RDP VMs

For my company, this means that GPUs such as the NVidia Tesla T4 GPUs will no longer accelerate VMs placed in Microsoft Hyper-V HA Clusters.