USB Boot Manager Won't Start A couple of weeks ago I booted a Mac Mini from a USB drive to install Ubuntu. Now I want to change it to Debian. I replaced Ubuntu on the USB drive. When I hear the boot chime and hold the option key, I get nothing on the display. If I'm slow in pressing the option key, it goes ahead and starts the installed Ubuntu image. I'm using the Etcher app to flash the drive. I also previously did it via terminal commands. I tried using the iso version of Debian and also converted it to a dmg. Neither work. If the boot manager didn't like the image on the usb, would it not come up?
The target machine is a late 2012 Mac Mini. I'm running the flash process on a Mac Pro with Big Sur.
This the file I'm trying to use that I got from the debian web site:
debian-live-10.7.0-amd64-standard.iso
I dug out an old Windows laptop. It's amazing it still runs. When I insert the USB drive, it doesn't appear in file manager or whatever it's called theses days. After a few tries, I got the boot manager and was able to select the USB Drive. I then saw a number of choices for installing Debian. I'm assuming the flash to the drive is valid.
I recommend installing the rEFInd boot manager as it recognises more OS's than those officially supported by Apple.
Once rEFInd is installed on your Mac it should present you with a list of boot options automatically each time your Mac is rebooted or powered on.