How can I install or activate an eSIM QR code received on my mobile phone?

On all eSIM-enabled iPhones (starting from 2018 and including iPhones XR, XS, SE, 11, 12, 13, 14, 15), if you have iOS 17 or new version you'll be able to activate an eSIM QR code received on your iPhone as follows:

1. Save the received eSIM QR code in your "Photos" on your iPhone
2. Go to Settings > Cellular (or Mobile Data) > scroll down to eSIMs (or SIMs) and tap "Add eSIM"
3. Tap "Use QR Code"
4. Tap "Open Photos" (shown below) and select the saved QR code to install the eSIM

Now you just follow the eSIM installation steps on iPhone.