Successfully installed Big Sur on legacy based machine.

Specs:

• CPU: i7-3770 3.4 Ghz with full cpu power management working;
• dGPU: MSI Gaming X RX 480 4gb with H264 and HEVC fully working;
• iGPU: Intel HD4000 with Quick Sync enabled and working;
• RAM: 12gb DDR3 1333 Mhz [2x4gb + 2x2gb]
• MOBO: Intel DH67BL with latest BIOS [Legacy]
• STORAGE: Samsung 850 Evo [MacOS] + Samsung 860 Evo [Windows]
• BOOTLOADER: OpenCore 0.6.8 [Legacy]

What's Working?

• Ethernet [Intel Mausi];
• Audio [Apple ALC - alcid=1];
• iGPU and dGPU [Whatevergreen];
• Bluetooth [USB Adapter];
• USB 2.0 [Front panel and back panel];
• Headphones jack - DP Audio;
• iCloud Services;
• All other things in macOS.

Bugs and things not working:

• USB Bug: when disconnecting and reconnecting a usb device in back panel it reboots;
• USB 3.0: Controller not supported and not recognized [NEC Renesas].

System Information

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EFI Structure