From what I have been able to puzzle out tonight, it looks like anything that you can place in /Library/Extensions, without a pre-existing copy being present in /System/Library/Extensions, can produce a usable prelinkedkernel using the Kext-Droplet application. Replacing pre-existing kernel extensions in /System/Library/Extensions seems to still be an unresolved issue.
I have confirmed that the Catalina Patcher copies of LegacyUSBInjector.kext, LegacyUSBVideoSupport.kext and even AppleIntelPIIXATA.kext can be installed with Kext-Droplet. However, I have had no luck booting into the recovery partition under Big Sur in order to disable authenticated-root to allow mounting a snapshot for replacing AppleHDA.kext and IO80211Family.kext in /System/Library/Extensions.
I tried the workaround suggested of copying Big Sur's csrutil so that it can be run under Catalina's recovery partition. However that failed as the Big Sur copy of csrutil seems to want to be run under Big Sur's rather than Catalina's recovery partition.
Some machines might try different prelinkedkernel, I uploaded some but other requires USBOpenCoreAPFSloader3 or to boot with CMD+S .
About Wifi if your Catalina mac uses AirPortBrcmNIC driver, then in my prelinkedkernel I embedded the IO80211Family.kext patched, so the stock BigSur Wifi I guess won't work in this case, for sound try some external USB or bluetooth speaker, for internal audio card MacPro requires a different AppleHDA.kext rather than the HighSierra one.
I doubt that third party system kext will work when installed in this BigSur path /Library/Extensions/
When you use my prelinkedkernel fix, to rebuild a kernel cache you should use this instead of kmutil:
kextcache -i / ; kcditto
For now from a non-APFS or legacy usb Mac you can't use an USB BigSur Installer or BigSur Recovery, but I am trying to make a patched one for BootKernelExtensions.kc and BaseSystem.dmg .
Without BigSur Recovery, to use "csrutil authenticated-root disable" you can use the ASentientBot patched boot.efi :
https://forums.macrumors.com/thread...unsupported-macs-thread.2242172/post-28604525
You should replace it here: /Volumes/Preboot/UUID-Preboot/System/Library/CoreServices/
dosdude1 advised to replace also in this path BigSurSystem : /usr/standalone/i386/
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Hi,
Big Sur loads fine now, but only loading from OpenCoreAPFSloader3
Works only with Apple bluetooth keyboard and mouse. We need a way to clone the working installation. Catalina doent's see BigSur Volume, and mount a volumes called "Update" and "BigSur - Data" . Disk Utility crashes (closes) after launch due to the Big Sur Container. I have try to clone it with BS recovery. it start, but then return an error. Wifi is still unavailable after patching. I have also tried to fix wifi with the new kext copied in /Extensions/ from BS Recovery, without errors but unsuccesfully (image attached)
When you applied the prelinkedkernel fix, from BigSur normal booting you should use
kextcache -i / ; kcditto
rather than "kmutil" that is only for BootKernelExtensions.kc .