Apple’s transition from Intel processors to Apple Silicon processors has introduced some differences in how Macs operate. Similar to Intel Macs equipped with the T2 chip, Apple Silicon Macs feature a Startup Security Utility that controls how disks are used as startup disks.

While there’s no option to allow or disallow external drives as startup disks, the settings require that the startup disk use either the currently signed operating system (similar to how iOS devices work) or a previously signed operating system. The traditional method of copying the operating system and then “blessing” it is no longer supported.

This means that any startup disk must be created using an Apple macOS Installer. As a result, bootable clones, as well as eDrive and Techtool Protogo devices in their previous forms, are not supported on Apple Silicon Macs. Consequently, the eDrive and Techtool Protogo tools are not available in the Tools category of Techtool Pro on these Macs.

The best solution is to install the macOS on an external drive and then install Techtool Pro afterwards. However, there are some important caveats to consider. Currently, the only drives that are 100% reliable as external startup disks are Thunderbolt 3 or greater SSDs. USB 3 drives may work in some cases, but it is still unclear how to make them consistently reliable as external startup disks on Apple Silicon Macs.

To ameliorate some of these limitations, the Volume Rebuild tool in Techtool Pro allows for live repairs of a volume while booted from the active startup volume.