I'm getting an error saying APFS disks may not be used as a bootable media. I have a USB that was previously formatted as MacOS Extended, and I reformatted it to APFS. I got the same message before and after reformatting it.
MacBook Pro 15″, OS X 10.11
A Bootable Installer of any version of macOS including the most recent version macOS 12 Monterey Requires the Bootable Installer be formatted as HFS Journaled with GUID Partition Map.
A Bootable Installer of any version of macOS including the most recent version macOS 12 Monterey Requires the Bootable Installer be formatted as HFS Journaled with GUID Partition Map.
Sorry, my bad, I picked an outdated platform (I have a few different configs). On the machine I'm creating the bootable USB I'm running High Sierra on a 2011 Mini with an i5.
If you are using Mac OS X El Capitan as indicated by your post, then no, APFS is not bootable and is probably not recognized as a valid disk format by the OS.
Mojave and all newer macOS versions can recognize the APFS format as a valid boot format. Any OS prior to Mojave, including High Sierra (?) must boot from a Mac OS Extended formatted drive.
Can't make APFS bootable?
