How can the check point on startup for macOS's T2 chip authentication be bypassed for securely signed OS's like RedHat? How can the checkpoint on startup for macOS's T2 chip authentication be bypassed for securely signed OS's like RedHat?

I know after both drives within, say macOS Catalina for example, are mounted while in the root bash of a recovery partition, you can edit almost anything in either volume, but how does one get to the "watchOS" prefs/executions, to add to or modify the list of "secure signed OS's" you can boot with, even after the OS Security pref has been set in that recovery window to allow external drive booting?

Apple keeps claiming on all official documentation and forums that you can install Linux to a T2 enabled machine, but it doesn't appear this is true of booting (post install, even if UEFI equipped).
You can set the security level for the T2 chip to allow the installation of Linux. However, if the Mac has internal drive (onboard PCIe-based SSD storage) which requires a driver that the version of Linux being installed does not have, then you will have to install to an external drive.

Apple has supplied a driver for Windows 10. This is included in the Windows Support Software which can be downloaded by using the Boot Camp Assistant. I am not aware of any version of Linux that has an equivalent driver.