Folks, I don't have a t2-equipped Mac yet.
But for all those who are still having t2-related boot problems, I'd like to offer a suggestion.
Try things "my way" for a period of one week, then go back if you like.
Here's what I suggest:
- Boot to the recovery partition
- Open the Startup Security Utility
- Under "secure boot", choose "No security"
- Under "external boot", choose "Allow booting from external media"
- Close Startup Security and reboot.
Yes, I realize this disables the t2 (insofar as it CAN BE "disabled" through user software).
But... again... give it a try this way for a week and see if it changes anything.
After all...
Macs ran well enough for 30 years without a t2 chip inside.
Speaking only for myself, I have no need for one now.