Is there a way to switch from Built-In speakers to HMDI audio output when an HDMI cable is plugged in automatically versus going through the settings?
If you are using pulseaudio
You can disable/mute the built-in audio and use the HDMI
You have to use pavucontrol to do that.
If you want to use all your audio simultaneously,
install paprefs and enable the simultaneous output
and configure your sound in pavucontrol.
then you can enjoy all your audio sources.