There was already a property for Mastodon instance links and addresses, but there was not one for Lemmy communities, but with that new property, you can create a statement with a Lemmy community ID for a certain item.
https://wikidata.org/wiki/Wikidata:Introduction
Using the recently created property https://wikidata.org/wiki/Property:P11947
in Wikidata, you can define Lemmy communities using the property above.
There was already a property for Mastodon instance links and addresses, but there was not one for Lemmy communities, but with that new property, you can create a statement with a Lemmy community ID for a certain item.