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• iOS: https://developer.apple.com/ios/universal-links/ (covers over 99% of all iOS users¹, who are on iOS 9 or greater).
• Android: https://developer.android.com/training/app-links/index.html (covers 65% of all Android users², who are on Android 6.0 or later).

In the event that a PSU does not have the app installed on their device, or if they have an older (or non iOS/Android, e.g. Windows Mobile) operating system, these methods will allow the PSU to be re-directed to a mobile web page.

...

Security considerations are addressed here: https://tools.ietf.org/html/rfc8252.

References

1. https://data.apteligent.com/ios/
2. https://data.apteligent.com/android/