Well, there's a few options out there for something like this, it depends on what you're going for specifically. There's Gemini and gopher, protocols designed

Well, there's a few options out there for something like this, it depends on what you're going for specifically. There's Gemini and gopher, protocols designed around transferring and rendering plain documents. There are terminal based browsers like Lynx that render pages in a terminal, of course it's all text on your end. If you're talking about a GUI program to do what reader view does and only that, the reader view code is open source and available from Mozilla, I'm sure it wouldn't be much to build a webview app for mobile or a simple GUI that sits on top of curl or wget or something like that, fetches the page, processes a URL and renders the text. You're probably going to be manually entering URLs though, I'm not sure in the modern web how you even click from one site to another, how you even wind up at a URL for a written article using only reader view.