The QR Block plugin provides a few blocks:

• QR: A block that generates the QR code based on its content. Generic purposes.
• Wi-Fi Network Connection: Connect to a Wi-Fi Network via a QR Code.
• QR Post: Share your post with a QR Code.

Also, it renders the QR code of the current post in the Post sidebar. A simple but functional way o load the post on mobile, for instance.

Source & Support

You can follow development, file an issue, suggest features, and view the source at the Github WPHackers/qr-block repo.

Credits

This block is powered by the brilliant qrcode.react library.