MicroSD-based USB boot manager for Pi?

Is there some sort of USB boot manager for Raspberry Pi versions
that don't have an EEPROM? I'm thinking of armv7 Pi2 and early Pi3.

Bootcode.bin on an otherwise blank msdos microsd partition works,
but seemingly only with a single USB drive connected. A second
USB disk left in place by mistake caused the machine to hang.

Something installed on a microSD that finds and reports bootable
USB drives, defaulting to the last one used, would be ideal.

This video from about 2016 suggests it's already been done:
https://www.youtube.com/watch?v=bNL1pd-rwCU

But, no implementations turned up in a web search. All the boot
manager references I found seemed to involve the Pi4. I'm interested
in using older machines already on hand. As it happens, most of
my machines run FreeBSD which uses u-boot as an intermediate step
but I don't think that matters.

Thanks for reading!

bob prohaska