When I playback video files with 48khz Audio (Tested with TrueHD and FLAC) on my iPad Pro 11“ 2. Gen and use my usb dac (Dragonfly Red) the Audio is being resampled to 41.1khz.
We have not done much testing with USB DACs, but this may be something we can look into.
Are you seeing this behavior in other apps like Photos or Files?
It works as it should in the VLC App and normaly iOS switches to the right samplerate automatically in other apps.