Hi @jssotomdz,
Did you see the note on the alsa-interface documentation?:
t’s recommended that most snaps access audio functionality through the system audio layer, such as PulseAudio, via the audio-playback and audio-record interfaces.
I have not checked if this helps with the DJ controllers though, but please note that not all hardware can handle multiplexing when being accessed directly through alsa (which is solved with the use of the audio-* ifaces), so granting the auto-connect of alsa might allow the snap to (inadvertently) block audio.
+1 from me for auto-connect of removable-media since as described most DJs store their music in external media drives.