You need to make the actual link be the displayed text for the instance agnostic link to work. The actual link in your comment is to https://sh.itjust.works/c/inktober when viewed from any instance.
If you type or paste !inktober@sh.itjust.works into the editor instead of trying to add it as a link it should make it a local link and the displayed text. For instance, this link works differently when I'm logged into piefed vs lemmy.
https://piefed.world/community/lookup/inktober/sh.itjust.works