Got Big Sur fully working on my MSI Z390-A PRO, Intel Core i5-9600K 3.7 GHz and AMD Sapphire RADEON RX 580 NITRO + 8GB : r/hackintosh
my second build. i5 9600k(5ghz oc), msi z390 mpg, rx 580 8gb(1500mhz oc),noctua nh-d15 and 650w psu. the case is a kolink observatory rgb it is a eu only case i think :
i5 9600k-Radeon RX 580-16gb Corsair RGB-500gb Samsung 860 EVO- Asus Prime Z370-a | eBay