Since it runs a desktop GNU/Linux, you can develop and run the same app on mobile and desktop with some adjustments in the interface. It already works well with Firefox and Gnome software.
This assumes the websites themselves don’t screw it up with a bunch of splash screens and gates to force users to iOS/Android apps. It’s not just an issue of Apple and Google having a duopoly, a ton of websites actively maintain the status quo and make it difficult for other players to enter the market. There really needs to be legislation to prevent sites from artificially locking users out of the mobile web experience.
Just as long as using the app store isn't required.