MacOS – Mac stuck at the loading bar, when trying to boot from macOS Catalina Patcher

For anyone facing this situation, the fix is this:

Note: This has been tried with a 13 MacBook Pro 2018 and 15 MacBook Pro 2018. This should work on any bricked T2 device.

Requirements:

1. Another working macOS computer (PC-1)

2. USB-A to USB-C cable or Thunderbolt 2/3 to USB-C

3. Bricked macOS computer (PC-2) that wont boot external drives and Internet Recovery is not working.

4. Apple Configurator 2

Step 1: Download “Apple Configurator 2” to PC-1 from App Store

Step 2: Connect PC-1 to PC-2, if your PC-2 is a MacBook Pro 2018+ (4 Thunderbolt ports), you need to connect the Power Supply to the LEFT TOP port of the PC-2 and the USB-C to USB-A to the LEFT BOTTOM port of the PC-2.

Step 3: Open “Apple Configurator 2” in PC-1

Step 4: While connected (step 2) power off PC-2 pressing the power button for around 5 seconds

Step 5: While off, press COMMAND+OPTION+RIGHT SHIFT+POWER until PC-2 appears in PC-1 as “DFU”.

Step 6: Once “DFU” appears in PC-1, select it and go to “Actions > Advanced > Remove Data & Settings”.

The drive will be wiped and an error will appear in PC-1 when trying to re-install macOS (THIS IS OK) and PC-2 will just restart.

Step 7: Disconnect PC-2 from PC-1

Step 8: Power off (if it’s on) PC-2

Step 9: Boot PC-2 with COMMAND+R, internet recovery should appear.

Step 10: If on wifi: enter credentials

Step 11: Internet Recovery will show a progress bar and a timer, follow the instructions and restore your macOS.

Internet Recovery failing happens because PC-2 detects more than 1 partitions in the hard drive, that’s why we wipe them out with Apple Configurator 2 and then try again to restore from internet.

I mentioned in the original post that I had reset NVRAM (twice, as it happens). I reset NVRAM a third time, and lo and behold, could now boot from the external SSD. Go figure.