I have no idea as to the status of userscripts on mobile devices but at least on the desktop they are my go-to for personalizing my internet:

    ("news.ycombinator.com" === window.location.hostname) &&
    (function () {
        var meta = document.createElement("META");
        meta.name = "viewport";
        meta.content = "width=device-width, initial-scale=1";

        if (document.readyState === "complete") {
            document.head.appendChild(meta);
        } else {
            document.addEventListener("DOMContentLoaded", function () {
                document.head.appendChild(meta);
            });
        }
    })();