Content Caching not working in macOS Mojave, Catalina or Big Sur

[vinaypundith]

I created a macOS (Catalina 10.15.7, Mojave 10.14.6 and Big Sur 11.6.2) virtual machine on my Proxmox VE 7.3 host using this guide: https://www.nicksherlock.com/2020/06/installing-macos-big-sur-on-proxmox/ (and the respective ones for Mojave and Catalina). My whole purpose of the VM is to serve as a local software update cache. But I cannot get Content Caching to work - it says "Registration Rejected" in the logs. I'm aware Apple blocks Content Caching from being used on virtual machines - however I have tried the kernel patch from https://github.com/ofawx/VmAssetCacheEnable and the other patch (for macOS 11.3 and newer) from https://github.com/acidanthera/RestrictEvents. Both do their job of erasing the VM compatibility block, and I do not get any related errors, but when I try to enable Content Caching, it says "Content Caching is temporarily unavailable" an in the Console logs it says "Failed to create context -44006" followed by "Registration Rejected".

What I've tried: Avoiding usage of vmxnet LAN adapter (instead PCIe passthrough-ing Intel 82574L), change OpenCore serial number (stuck with iMacPro1,1 SMBIOS though), above patches.

Does anyone know what's up with this? I assume maybe something in my OpenCore setup (taken exactly from link in the above guide, I can't seem to find any other guide). People seem to have had luck with this, but no one has posted what their setup process was like. I don't care if I have to downgrade macOS or OpenCore or anything, for this to work.

Thanks in advance!