When I read technical journals often in PDF format on my Mac (Monterey), I notice that URL links are sometimes provided as a QR code only instead of a clickable link.
The only way I found to open the URL on my Mac is to turn handoff in both my iPhone and my Mac > take picture with my iPhone > open the handoff URL in my Mac.
The whole exercise is absurd because the QR code is in my Mac to start with.
There are free QR code readers apps, but they seem a bit suspicious (free and a lot of marketing).