Just get yourself a little CardReader with a lightning port or a lightning port USB stick.
There’s one from RAV-power with 64GB internal storage and the card reader accepts cards up to 256GB.
It has a USB port on one side and the lightning port on the other side which makes cross-platform sharing or re-filling really easy and the playbacks stream right away from the dongle. Well, I know it’s another piece of gear to think of, but for all the above mentioned reasons I never leave the house without it.
Got my whole music library on a 256GB card so it serves also as an additional backup for my music.
When you’re running out of space on your iPad just move two or three 4k files over to the stick and you got yourself some GB of storage available in a minute
IIRC it was about 40€ (without a card obviously) but 64GB internal storage. It’s not cheap seen from a GB/buck ratio but as iDevice users we have to deal with all these hurdles. That’s just one more hack