"Solved" Found how to remove the thunderbolt driver in Big Sur this morning. In Catalina, deleted drivers were not loaded by the kernel at boot after having deleted/moved/renamed the kext directory. In Big Sur, The driver remains in the extensions cache, this one must be rebuilt with kmutil You must "deactivate the seal" and make another snapshot after the cache has been rebuilt. Follow this procedure : Reboot in rescue mode (reboot while "Cmd + R") csrutil disable csrutil authenticated-root disable reboot in rescue mode mount -uw /Volumes/[MacOS <your custom stuff here>] delete (or rename, or move elsewhere) the AppleThunderboltNHI.kext directory (I've moved all thunderbolt kext directories since I have no needs about this interface, but I think it works only by disabling AppleThunderboltNHI) REBUILD the extensions cache ! (new has-to-do in Big Sur...) : kmutil install -u --force --volume-root /Volumes/[MacOS <your custom stuff here>] DON'T FORGET to create another system snapshot to take these modifications under account at next reboot : bless --folder /Volumes/[MacOS <your custom stuff here>]/System/Library/CoreServices --bootefi --create-snapshot csrutil enable (mays be you have to reboot in rescue mode.. not tested) Finally, reboot in normal mode : you can check kextstat : it shows that the driver is actually not loaded :) It works for my MacBook Pro mid 2014.. Either a hardware problem when using the driver of the host interface, either a bug. Apple did not communicate, I think it's a hardware issue..

Hmm, I do not encrypt my Mac. I think if you want to encrypt, you have to disable FileVault in system preferences, follow the procedure, and then enable FileVault. Remember : you have to do that at each big sur update.. Unless Apple fix this bug or you buy a new Mac (M1 ...)

This shutdown occurs when the Mac seems to use the discrete graphics, and is hot. I had yesterday to invoke 'kmutil invoke-panic-medic' to disable all third party pbs, and check the integrated graphics was used (kill chromium etc..) So : in recovery mode, kmutil invoke-panic-medic, ensure your integrated graphics is used rather than nividia, you should have enough time then to disable FileVault

It sucks...

You have to mount '-uw' your system partition where you are in rescue mode. Sometimes your system partition is called MacOs, or Macintosh HD, or MaOS blabla, depending on your installation options and when you have installed your Mac. In your case, it's juste fine (Macintosh HD) is a well known default name for the system partition.

To @McQueen69 (and all), You should always : Consider It's tested for a mid 2014 MacBook pro (the ones that are well known to be affected by this pb). I can't know what other Macs do with the thunderbolt interface (dependencies, ..) As a good manner, back up your Mac or your very important files before (especially if your storage is soldered) unplug all unnecessary devices Always have a USB install key prepared (you can do this before installing Big Sur, with the "sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume" procedure Now : @McQueen69 : model of your Mac (13, .. ) ? It's very weird, since this procedure does not affect at all the rescue area. Are you sure you have done your mount and snapshot as I said to the "system partition" /Volumes/xx ? unplug all thunderbolt devices plug an external wiped storage device, a USB installation key, then boot + "C" at startup, reinstall MacOS on the external device and mount your system partition to back up the users files. Then reinstall from scratch (Catalina) on the internal storage. It should work, I don't think you can actually brick a Mac.. At last resort, the Genius Bar should help.

@mergenc : the « custom stuff » is the name of the Volume int /Volume that holds your OS. I can’t be more precise it depends of your history (for me it’s /Volume/MacOs because I’ve reinstalled from scratch for Catalina. Before it was called /Volume/Macintosh HD if you installed old OSes) Again, backup before, usb media near you, external device is a plus.. Sorry for the reply delays : I’m in France 😎

@mergenc : you’re right : I told to only « csrutil enable » at the end of the procedure, not to « csrutil authenticated-root enable » You can’t do that in Big Sur if you modify the Os (because new files you have generated like the extension caches are not signed by apple!). I’ve not explicitly warned about that in the procedure, I will update it this evening It’s described here in the details : https://developer.apple.com/news/?id=3xpv8r2m ... you are only disabling the NEW security functions but you keep those functions that were part of Catalina I don’t know if Apple will let us continue to workaround this bug or hardware issue in the future updates or to let us with older versions of macOS until we decide to buy a new Mac ☹️ Finally I don’t know if the future Big Sur updates will run as expected 😬. We will know soon as usual ... Have a good day in Mongolia 🇲🇳