Too many bad assumptions on your last reply:
01) I do not use MacBook references in my configuration, all my work recently has always been MBP13,1 or MBP13,3.
02) My kext order is correct per the guide, always load Lilu first, then the other masters, etc.
03) My machine is NOT a Dell - Dell bought Alienware one year AFTER I purchased this machine. But still, this morning I assumed it was a Dell and made the SMBIOS changes you mentioned anyway.
04) Yes, my machine is the 4K UHD model which is what I have been stating from the start. All of the guide and internet references for my machine AAPL-id (191B) have 1080p display numbers in their examples, never the 4K numbers which I assume are a little different. The only info I could find for 4k was adding '-igfxmlr' in the boot arg and that doesn't help either way.
05) My DVMT is not changeable, no setting in the BIOS - Alienware would not make my life that easy, lol. If so, I would set that variable in UEFI to 96MB or 128MB and away I would go happy
This morning I put in your SMBIOS setting changes (true/custom/etc) and laid that change out in ALL of my config.plist variations. I even took your suggestion for MBP13,1 instead of MBP13,3. No difference at all. So here are my config variations at this point. All other WhateverGreen variations are a waste of time.
Config02 (0x00001619)
Config05 (0x00001B19)
Config14 (0x06001B19)
Config2, no Metal acceleration, always 31MB in AboutThisMac.
Variations are no good either. On the second boot when it panics, power-down and power-up are required, no courteous auto reboot done by the system.
Config5 - first boot always works, variation spoof 1619 will get you a desktop without acceleration and the 31MB setting, every repeated boot.
Config14 - first boot always works, variation spoof 1619, same deal. My machine does not like 1619 at all. I'm still not done with this config14, because in AboutThisMac, it always displays a "Revision 6" on my 1B19 resource, and this "6001B19" may have something to match up with that? Plus, it is one framebuffer connector built-in which is what my laptop is, a notebook display only. HDMI on my machine is for the NVidia GPU. I don't know what the 3rd connector is for on my configs, except for more confusion.
Config5-Try - my last attempt, taking away connectors thinking it is confusing the framebuffer. Same result, one boot great, second boot will panic and reboot. Windows boot required as usual.
After 250+ reboots in the last few weeks and all the config variations I have tried, I'm convinced it is something in the AppleIntelSKL kext that just doesn't like my machine, and something in that kext changed from HighSierra to Mojave, and whatever that change was - it has remained constant all the way up to BigSur. A few years ago when I was trying to get Mojave installed when it was the current flavor, I had the typical stuck at IOConsoleUsers problem. All the experts over at TonyMac, InsaneMac, etc could not figure it out. All of them said the same thing "your machine should be working.....", and downgrading to HighSierra with the SAME settings made it boot right up without issues.
My last ditch effort on this fiasco will be attempting to boot off of my HighSierra SSD stick plugged into a USB port. If it can do that, I will go into the System folder extensions and copy every 'SKL' kext directory and push them over to my BigSur System folder just to try and force the system to use the old SKL stuff. Might work....probably won't, but worth a last attempt try.
Just for reference, here are my CURRENT config files and variations with your suggested changes in them.
Thanks,