This is a terrible solution. Now you require an Internet connection and a (non-abandoned) third party service to configure a LAN device. Not to mention countless industrial devices where operators would typically have no chance to see QR code.
It might be easier to extend the URL format with support for certificate fingerprints. It would only require support in web browsers, which are updated much faster than operating systems. It could also be made in a backwards compatible way, for example by extending the username syntax. That way old browsers would continue to show the warning and new browsers would accept the self signed URL format in a secure way.