But do you want to use Ionic without any framework or just don’t use Ionic to build your app?
You can use Capacitor to build your app and use any framework or none at all.
If you want to use Ionic but without a framework, not sure if there are any “getting started” docs, but all ionic components have “vanilla javascript” instructions, so I guess you just need to npm install @ionic/core and read the docs for the components you want to use.
If you want to use Ionic, you would need to use Capacitor or Cordova as both of them use WebViews to display the frontend, that’s not possible on Qr nor Xamarin, unless you plan to use them and just use the WebView component they probably provide.