Maui for macOs only builds Catalyst apps (IOS apps run in a sandbox). They will have access to a mounted USB filesystem, but not direct access to the device. you can use the "mount" command to see the usb device and volume path. example of msdos formatted usb plugged in to Mac:
/dev/disk14s1 on /Volumes/NO NAME (msdos, local, nodev, nosuid, noowners, noatime, fskit)
when you plug in a usb, it auto mounts and the filesystem shows up on the desktop. the device was /dev/disk14s1, and the filesystem was mounted on /Volumes (the default mount point).