I think you can just pretend to be a PWA, no need for code changes.

You may need an unused service worker, or not, I don't remember.

This just means your site looks like an Android app (but still needs net, etc).

Thanks, I used to do something like that when I made a tabletop like card maker using three.js + angular 8, but it has been a long time ago, I need to catch up with the details how to implement it with angular v21 since it is almost a completely new framework compared to the old versions