Thank you for your post. Unfortunately, that is something that we have never tested. Theoretically, it should work because we do support SD cards with the Android app and you can import maps through your Files app on iOS devices.
I don’t know if it will be found under “On My iPhone/iPad” or if it will pop up as its own location. Of course, there is no harm if you want to try it, but I can’t guarantee that it will work.
If you have tested it and it doesn’t work then it may not be possible. Let me know the results if you have tested it.