I remember I could install Linux with Boot Camp, but that was some time ago, my memory may be faulty, and Apple’s Boot Camp support has disappeared in recent years. Boot Camp support ends with the end of Intel-based Macs, which means that not much effort has been put into keeping it up to date, and there is nothing I have seen that suggests a similar technology for future ARM-based systems. .
Is there a reason to double boot as opposed to using a virtual machine? I gave up dual booting a very long time ago. At that time, computers became cheap enough and reliable enough that I could afford to have an old computer (or seven) around to run the operating system I want and avoid the need to restart. There have also been significant advances in virtual machine software. I now routinely run one or two virtual machines on my newer computers. This let me browse between Linux, macOS and Windows with a key macro instead of having to restart or go to another computer. This ability to run multiple operating systems also comes with the speed, low cost and durability of modern computers.
The problem with the T2 chip and running Linux has little to do with rEFInd. The problem is that only the T2 chip is activated, only signed operating systems will start. I do not know if Apple prevents Linux from being signed, no one bothers to go through the process of signing the OS / kernel / whatever, or why the two do not meet.
Until there is a Linux OS that is “blessed”