WebFinger is not a simple static file (though of course it can be). The URL has to respond based on the acct provided in the query parameter. So, each user needs to have their own links .
For the moment, it's best to use something like https://wordpress.org/plugins/webfinger/ . Or if you can code, just write some simple PHP page or static Surfer page to respond . Cloudron's nginx server will query the app.
