Everything is working; sleep, USB, sound (dodgy way there!). Even Checkra1n doesn't have any problem with detecting your iPhone in DFU mode.
Installation
First-time installation
First of all, go to the UEFI settings and disable the serial port. Upgrade the BIOS to the newest possible version (currently the newest version is version no. 00.02.56, Rev.A which was released on the 30th of April 2019).
Copy OpenCore to EFI partition or USB drive. In contrast to Clover, you need to have BOOT\bootx64.efi file.
Simply put your Big Sur install USB into any port and select Install macOS option in OpenCore.
Issues
VGA Display output isn't working
TV app is working but it is not stable at all. Sidecar is not working.
VoodooHDA... Can't get AppleALC to work. OpenCore documentation is just a piece of sh*t.
Credits
OpenCore with Big Sur support config was created by bieleckipawel;
