How Intel Macs with T2 chips, and Apple silicon Macs can be rescued from the apparently dead by connecting them to another Mac in DFU mode.
DFU port
One Thunderbolt port is the designated DFU port, to be used when connecting via USB-C in DFU mode, and to be avoided for external bootable disks. But how can you identify it?
Apple silicon Macs were designed to boot almost as securely from external disks as from their internal SSD. That makes macOS installation a little more complicated. Here’s how to do that.
It took over 6 months before creating bootable external disks was fairly reliable, and even then there were unexplained failures. Did someone fail to tell us something?
Two important catches that can cause a macOS installation to fail in Apple silicon: using the DFU port, and not setting up ownership correctly. Both are explained here.
Some support USB4, others don’t. Some share the controller, others don’t. Some support DFU mode but then can’t be used to create a bootable external disk on Apple silicon.
The Eclectic Light Company 