It sounds to me like the problem is some breakage in the MobileDevice framework, which is linked via CoreAudioKit, which in turn is required for AudioUnit UIs and Bluetooth MIDI support. Therefore, I’d expect all AudioUnit plugins with a custom UI to be affected, but other formats (AAX, VST3 etc.) may only be affected if they link CoreAudioKit. If your users have functioning AudioUnit plugins, then either there’s a way to use CoreAudioKit without triggering the break, or there’s a way of avoiding the CoreAudioKit dependency altogether for some AudioUnits.
Can you find out whether your users have functioning third-party AudioUnits?