Mac should be able to read Fat32, and so should the Deck. You should use a universal drive format when possible, not whatever each one recommends (probably HFS or APFS for Mac and ext4 for Linux).

If you’re trying to install Windows on the Deck via Mac, you might need to create a virtual machine first with Windows on it:

www.microsoft.com/en-us/software-download/

Or possibly Linux (which you could probably do via the Deck, too):

linuxiac.com/how-to-create-a-windows-bootable-usb…

I did read that the WoeUSB program mentioned in that article might also work on Mac, but I can’t verify if that’s true. Option three is to ask a friend to create a Windows Media USB for you.