HALLE-LUJAH!!!If you haven't disabled CSM (legacy option roms) and set to UEFI booting only the 580 won't work. You also need to have Whatevergreen and Lilu kexts installed properly to L/E/ if you are using that instead of injecting all kexts via Clover.
Thanks for this, it fixed my broken audio too. Very happy !New Optiplex 3020 SFF Big Sur Guide
Just finished posting this if anyone is interested in switching their 3020 to OpenCore and Big Sur.
I'd suggest a clean install, especially if you're not using iMac 15,1 SMBIOS. If you don't want to clean install make sure to remove all hackinosh kexts from /L/E if you have any there. Clear NVRAM before switching to an OC EFI.
Dell Optiplex 3020 SFF with Core i5 CPU Components Dell Optiplex 3020 SFF Amazon - Newegg LG 27" 4K Monitor Amazon - Newegg 240 GB PNY SSD Drive Amazon - Newegg 2 x 4GB Timetec DDR3 Ram Kit Amazon (2 x 8GB kit also available) Active DP to HDMI 2.0 Adapter Amazon Active DP 1.2 to HDMI...www.tonymacx86.com