Finding the QR code and scanner in #amethyst was somewhat hidden, once found though (not too long) it worked.

It could be part of a "view a shared not or profile" and "share note or profile" navigation flow. Amethyst has the latter one, as it's on the profile view, both in the left side drawer and profile view page. However, it wasn't clear there was a scan option for the QR code on the left side drawer, unless you open it. Perhaps a camera icon next to the QR code could show there is also a scanner. It could launch directly to the QR code scanner and then toggle between the two.