What is said in the wiki is only partly right
I just did some experiments, it was a bit variable, armbian I think
My setup is perhaps unique, emmc uboot blank, for this mrfixit uboot on blank SD
So, I can't say anything about other uboot versions
Somewhat reliable booting from usb3,, no boots at all from usb2
Both usb3 and usb2 sticks
And, never a boot from uSD in a carrier/dongle
--edit--
If you really want to know, uboot order is called "target",, so...
strings u*boot*|grep _target
And, you can always "yank" uboot out of media, starts 8M, about (or<) than 2M long,, so..
dd (appropriate if,of) bs=1M skip=8 count=2
I just did some experiments, it was a bit variable, armbian I think
My setup is perhaps unique, emmc uboot blank, for this mrfixit uboot on blank SD
So, I can't say anything about other uboot versions
Somewhat reliable booting from usb3,, no boots at all from usb2
Both usb3 and usb2 sticks
And, never a boot from uSD in a carrier/dongle
--edit--
If you really want to know, uboot order is called "target",, so...
strings u*boot*|grep _target
And, you can always "yank" uboot out of media, starts 8M, about (or<) than 2M long,, so..
dd (appropriate if,of) bs=1M skip=8 count=2