I had the same problem. Glad I found your post. FYI its under (Standard system devices) from the left tab.
So how do you know it's ACPI Processor container device??? After I did what you've suggested, the device remains in the Other devices -> Unknown device
That's rough.
From what I understand, you're "tricking" it by using another card, but then you'd have to have another card to use.
I dont really know what I'm talking about, but I can confirm that passing through RX580 (only GPU) is working on my setup. I left detail notes in the other thread