Framework for Mobile Responsiveness

Hey guys;

What’s the best way to create a mobile responsive type application? We have a full desktop app and are looking to basically create a mobile browser version that appears like a mobile app but isn’t. Is the best way to redirect to the mobile version based on screen size and use Vue.js UI components, or do we try to determine Android vs iOS and then provide native browser components? Or are we better off just making a mobile app at this point lol?

It all seems a bit messy, help would be appreciated 🙂