It’s also my first time using Greasemonkey – as far as I understand, it just opens a popup window whenever you open a “.user.js” file that allows you to install the script. So just downloading Greasemonkey and opening the raw .user.js file from Github does the trick.

You need so search for it (!hardcore@lemmy.ml) on your instance (lenny.world). The search won’t yield any results but will trigger a request to lemmy.ml and it should become accessible / appear in searches a moment later.

Firefox on Desktop, with a Greasemonkey script to improve the UI a bit.