Took me a couple of weeks to solve my 11.3 issues. There was a lot of hassles, especially with ACPI (Fn F9 - ACPI boot menu) losing the boot menu for Opencore and Fedora, repeatedly. The best way to fix the loss of the menu in ACPIThis has been solved by a combination of opencore 0.6.8 and an additional kext - FakePCIID_XHCIMux. I also changed the XhciPortLimit to False. I am still running USBInjectAll.kext. I have always had a problem with a failure of this machine to cleanly shutdown, complaints from BIOS on restart. This has been fixed by applying the RTC patch to DDST using MaciASL.
Finally, I have got my grub menu successfully chainloading OpenCore from Fedora. If anyone interested I can post the information here.
Still a little shy to upgrade to 11.3.1 probably wait to official 11.4. And eventually I will get the time to try and get the touch working....
Peace
Calan