usb drive not readable

Etcher version 1.19.21 on MacBook Pro 2021 Sonoma 14.6
attempting to use usb drive for linux mint installation on Mac. linuxmint-21.3-cinnamon-64bit.iso
Flash completed successfully
but then message saying ‘disk you attached was not readable by this computer.’
tried two different usb, both same result. can’t find a way to initialise disk or solve the problem.
new to this…
any suggestions?