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