So it turns out that the image works fine in Monterey, but due to the security features added in Catalina, there are some extra steps to make Disk Utility and Terminal work properly. In System Preferences > Security & Privacy > Privacy > Full Disk Access, add the following applications to the...
This means that it began booting, so the partition type is likely correct, but once the macOS kernel took over it couldn't read the USB drive. I would try a few things:
Try the drive using a powered hub (that's what has given me success)
Try another USB drive
Ensure you used the correct start...
As you may know, the firmware for the 1st-generation Apple TV was a modified version of Mac OS X Tiger. Back in the day, many members of the Mac community were able to get full versions of Mac OS X running on the Apple TV. Unfortunately, patched disk images with the fruits of their labor have...
I have a 440BX system with a Voodoo3 3000 AGP in it and it works great! FWIW, I had problems getting the card running properly until I installed the 440BX chipset drivers.