Original post, containing the original code @soy@lemmy.world made: https://sh.itjust.works/post/33762

his original message:

For those that use Tampermonkey or GreaseMonkey, here’s a quick script I whipped up that creates a button that redirects communities from other instances to your local instance. If your instance isn’t lemmy.world, then change the localLemmy var at the top. Enjoy!

My small fix:

For personal use, I changed localLemmy to sh.itjust.works because that's my instance. I also embedded some styles and made it so it's top right instead of bottom left, and so that it's red and works better for me. Soy's original code didn't work for me so I had to make these small alterations to get it working.

// ==UserScript==
// @name         Lemmings Fix
// @version      1.0
// @description  Redirect to your local Lemmy instance
// @author       @lemmy.world/u/soy
// @match        https://*/c/*
// @icon         https://join-lemmy.org/static/assets/icons/favicon.svg
// ==/UserScript==

const localLemmy = "sh.itjust.works";
var isLemmy =
  document.head.querySelector("[name~=Description][content]").content ===
  "Lemmy";

if (isLemmy) {
  // Get URL info
  var splitUrl = location.href.split("/");
  var instanceUrl = splitUrl[2];
  var community = splitUrl[4];
  var localizedUrl =
    "https://" + localLemmy + "/c/" + community + "@" + instanceUrl;

  // Create redirect button if not on local
  if (instanceUrl !== localLemmy) {
    var zNode = document.createElement("div");
    zNode.innerHTML = "Open in local instance";
    zNode.setAttribute("id", "localizeContainer");
    // add styles to the button embedded
    zNode.setAttribute(
      "style",
      "cursor: pointer; padding: 16px; background-color: red; border-radius: 10%; border-width: 3px; border-style: solid; padding: 3px; z-index: 10;max-width:200px;position:fixed;top:0;right:0;"
    );
    zNode.addEventListener("click", onLocalize);
    document.body.appendChild(zNode);
  }
}

function onLocalize() {
  window.location.replace(localizedUrl);
}