https://www.qr-code-generator.com/solutions/wifi-qr-code/ can build one, this is cool.

Android has this feature for a long time. Share the QR code even with iPhone users. And it will add them to the wifi

The best part is that you can generate the QR code from your phone. It's a button in the wifi settings. Really easy way to share it from one phone to another.

Is it on the iPhone too?

You can also read the QR code from your Linux laptop.

Install zbar-tools and use zbarcam from the command line. It will read the QR code using the webcam, and now you have the Wi-Fi credentials.

Or any other data in the QR code.