Please note that this method is still in beta, and might have unexpected or undocumented results.
Download and install from the Steam page
Varjo Base Download
Epic Games Launcher Download
Open Epic Launcher.
Go to the Unreal Engine tab.
Install UE 4.23.
From the System tab in Varjo Base, Enable OpenXR.
Open your project using UE.
From “Edit”->”Plugins” find OpenXR plugin and enable it.
Press “Restart Now” to apply changes.
From ”Built-In”, “Virtual Reality”, Disable SteamVR plugin, to make sure that the content runs against the OpenXR. Click “Restart Now” to apply changes.
To run on the headset or in Varjo software emulator, select “Play” → “VR Preview”
Tune the project with the guidance from Performance and Visual Quality page.