I have Big Sur 11.4 running just fine on an Alienware R10. I'm using my ancient geforce 730 1GB until my RX 6900 XT is delivered. the RTX 2080 Super it came with wasn't macOS compatible, of course. I seriously just used the OpenCore guide under Linux and macOS installed just fine from USB. So far Messages and the app store work. The wifi and bluetooth are a no go since they are a atheros chipset (I've not put any effort into getting them to work honestly). Audio works via AppleALC.kext (I haven't tested microphone input). Ethernet is Realtek. Im not sure about sleep or wake up.
Some weird quirks about this machine are the PCI-e 16x slots run at 8x speed @ PCI-e 4.0, I think this system is really intended for dual gfx cards. The chipset is not the AMD X570 chipset Windows reports. It instead is the B550A which is a kinda sorta rebranded AMD 470 chipset.
My system has the following hardware in it
R10 chasis
Ryzen 3900XT
32GB Kingston 2933MHz ram (actually 3200MHz RAM but is locked to 2933MHz)
32GB of some other 2666MHz RAM I had sitting around. Set to XMP 2 in the bios to run at 2933MHz.
PM981a NVMe Samsung 1024GB, PCI-e 3.0 (Linux install, i've read macOS doesn't like samsung m.2 drives)
WD 500GB SATA SSD (macOS install)
WD 3TB NAS hard drive
Most USB ports work in 2.0/3.1 speeds. I haven't tested every single port though.
Geforce GT 730 1GB (strangely works really well)
EDIT: Just tested sleep and wake up. Much to my surprise it worked properly.