There are issues on iOS when launching Cubasis 3.4.1 with Bluetooth earbuds (Devialet Gemini in my case, but i guess some others too ; i have an iPhone 11 Pro / iOS up to date) :
Earbuds connected, i launch Cubasis 3, there’s a pop-up saying the sample rate has been set to 16khz, so i need to go to the audio settings, activate Bluetooth / Airplay mode, open that Bluetooth / Airplay list to select the iPhone and select the earbuds again (to fix an issue with the buffer setting otherwize), then set the buffer to a correct value, close the project and open it again (to fix potential issues caused by the 16khz initial state). And then … the projects sample rate can only be set to 44.1khz.
The thing is that other apps work with these same earbuds at 48khz without issues.
Fortunately there is a workaround by launching Cubasis via Audiobus (or AUM, …) i thought it would be useful to mention this anyway…