How to mute ALL system sounds on iPhone 13?

I have my iPhone 13 set to silent mode (volume turned all the way down for ringtone and alerts) and turned the physical volume buttons on the side of the phone all the way down (as far as I understand this control applies to media volume?).

Under the settings for “system sounds and haptics” there are only the following three subheadings:

1) Keyboard feedback - which I have set to “None”

2) Lock sound - which I have toggled off

3) System haptics - which I have toggled off

But my phone still plays a sound when I plug it in to charge, or when I confirm a download in the App Store.

Please can someone tell me how to mute all of the sounds on my iPhone?