I have done multiple exercises on Multiple SMBIOS's and EFIs for our builds as I had a Sapphire RX 580 Pulse 8GB and I just bought a Radeon Vega 56 two days ago.
To save you all some time (and keep @AudioGod from having to answer multiple times about DRMGate) I am posting the report:
The Verdict for macOS Catalina (10.15.2) with latest Lilu (1.4.1) + WhateverGreen (1.3.6 - latest commit 79398ee) pulled from the master branch is:
Polaris Cards (e.g. Radeon RX580):
The only thing you can get is Apple TV(+). Netflix and Prime Video as well as other DRM protected content does not work on Safari. You can try other browsers like Chrome or Firefox where you will be able to watch, but the resolution is not Full HD.
To get Apple TV(+) you need SMBIOS iMac19,1 (@AudioGod's latest RX Polaris EFI is perfect) and instead of shikigva=80 use:
You will have Apple TV(+) working and NO CRASHES when trying to play DRM content on Safari. It will just not play, it won't crash.
Navi & Vega Cards (e.g. RX 5700XT, Vega 56, Vega 64):
There are two different routes you can go:
Use SMBIOS iMac19,1 (the latest and greatest by @AudioGod is perfect) and leave shikigva=80 boot argument as is. This way you'll have Apple TV(+) AND Netflix on Safari. Amazon Prime does not work (the webpage reloads on a loop saying there was a problem) nor other DRM test streams (e.g. the BitMovin) which is a bummer but WEG development is in a good way and I think our patience and the developer's hard work will give fruits sooner or later.
Use SMBIOS iMacPro1,1 (the last iMacPro1,1 EFI by @AudioGod is perfect even if it is not using ocQuirks but you can also get @AudioGod's latest iMac19,1 EFI and change the SMBIOS information and remove the shikigva boot flags using Clover Configurator) and disable your iGPU. You will have Apple TV(+), Netflix and Amazon Prime Video working on Safari in HD, but:
SMBIOS iMacPro1,1 is not the Perfect match for our hardware and Power Management is not close to Coffee Lake CPU as the iMacPro1,1 is packing a XEON
You lose SideCar (which might not be that big of a deal, but it is noteworthy)
Other DRM test streams still not work (e.g. BitMovin Demo or EzDRM) which means it is not as perfect as it seems.