Actually you can backup MOST of what you want like your photos, documents, contacts, videos and read the same content as well. You would think people would do some research.
Leef Mobile Memory how about this device or SanDisk iXpand
https://www.sandisk.com/home/mobile-...storage/ixpand or how about Mophie Space Case all of these options will give you the ability to offload and read from these storage options.
While not a microSD as you wanted its offers as close as you will ever get with Apple products.