Just to let you know: iOS13 has full support for USB sticks. You can access them through the Files app. ST3 can fully utilize this feature. That means you can restore backups or import songs from USB sticks. This might be the quickest way to transfer large libraries between devices.
If you get a message that a stick needs too much power to use, you can connect a powered USB hub between your iOS device and the stick.
I tried lots of different sticks and got all to work through the powered hub.