Olivier A USB-c to mini jack adapter works fine. I have used apple, but the strongest and best is a Swedish brand called Linocell. They both work fine. I have not tried an adapter that also charge the iPad, but I started out using a OSB-C to USB 2.0 direct to my mix. That did not work well. Got the same problem that you describe.
I have tried several Bluetooth receivers, Fiio and Xvive, neither could be trusted. The songs would all of the sudden stop for a millisecond, and then start again. Not useable for for gigs.