Ich habe dein Script mal erweitert, nun fügt es neben einem hinzufügen Link auch einen öffnen Link hinzu.

// @name         Add Remote Community Link to Lemmy Descriptions
// @version      0.4
// @description  Add a link to a remote community description in the form of "https://home.tld/c/community@remote.tld"
// @author       SomeDude
// @author       NoXPhasma
// @match        https://*/c/*
// @match        https://*/post/*
// @match        https://*/comment/*
// @grant        none
// ==/UserScript==

window.addEventListener('load', function() {
   const home = "feddit.de";
   const communityDescription = document.querySelector(".alert.alert-info");
   if(communityDescription) {
     const openOn = communityDescription.textContent.match(/!(.*@.*)/)[1];
     const searchOn = communityDescription.textContent.match(/(!.*@.*)/)[1];

      // Create the remote community link
      const remoteCommunityLink = document.createElement("a");
      remoteCommunityLink.href = `https://${home}/c/${openOn}`
      remoteCommunityLink.textContent = `Open on ${home}`;
      remoteCommunityLink.target = "_blank";

      // Append the link to the community description
      communityDescription.appendChild(document.createElement("br"));
      communityDescription.appendChild(remoteCommunityLink);

      const remoteSearchLink = document.createElement("a");
      remoteSearchLink.href = `https://${home}/search/q/${encodeURIComponent(searchOn)}/type/All/sort/TopAll/listing_type/All/community_id/0/creator_id/0/page/1`
      remoteSearchLink.textContent = `Add to ${home}`;
      remoteSearchLink.target = "_blank";

      // Append the link to the community description
      communityDescription.appendChild(document.createElement("br"));
      communityDescription.appendChild(remoteSearchLink);
  }
}, false);