On Android, there's Instant Apps[1] though for some reason Google hasn't integrated them on all devices. They work through links/QR codes and through NFC tags. I believe they might also be accessible though the Google Bluetooth Le beacon API (so when you enable the specific feature, you'll get a popup like "this location serves the following app" which you can then instantly launch).

I don't know about iOS but the two copy features from each other all the time so Apple probably has it too (if they weren't the first to launch them).

Honestly, if you're working from a QR code you might as well just serve a mobile web app. If you add PWA support your customers might even install it if they come around often.

[1]: https://support.google.com/googleplay/answer/7683278