PenciDesign replied
Hi,
For back-end - it's not needed favicon because WordPress don't render favicon inside backend. No readers view your backend.
For AMP, as I see you're using an AMP plugin, so you should check AMP settings from that plugin to know how to set a favicon for your AMP pages. Because on the AMP, the <head> will be re-build from AMP plugin itself and it does not depend on the theme.
Best Regards,
PenciDesign