Why does the poppy not see the boot part of the flash drive when booted?

Question

Iron

Hello everyone,
I allocated 10GB on a flash drive for Linux, uploaded iso there through the terminal without errors.
The Mac stopped seeing this part of the flash drive in Findcre, what about the fact that this part is bootable.
When I reboot the poppy and press the option, I see only the Mac hard drive, but there is no flash drive (that is, its boot part)
Why?

Answer 1

Hi,
Most likely, when "filled in iso through the terminal" the bootable structure on the flash drive was not created. Filled it with what or how?