Wow, sleep is actually working for me in Big Sur beta 10, even with my 12 USB devices plugged in. I didn't have to change anything for it to work, nor in EFI, nor in BIOS. No USB mapping done at all. Just a heads up for Catalina users that struggle to get it working. GPU fans go full speed for like 15 seconds after wake but that's probably a VBIOS quirk or something that can be fixed.