I don't have stock Android on my phone so this may be a feature my manufacturer has added, but I'm pretty sure you can press the shutter button instead of click

I don't have stock Android on my phone so this may be a feature my manufacturer has added, but I'm pretty sure you can press the shutter button instead of clicking on the popup to open the QR code. Also, as others have pointed out, with Firefox you can scan and open a QR core in two taps, so no need to go to the camera app at all.