Right now the strategy is “sit there and hope it catches on” so… open to really any suggestions beyond that.
It’s not a niche community, so it’s both harder and easier that way - you can’t promote it in any niche communities, but it also has somewhat broader appeal.
Here are some ideas (don’t spam):
Make YouTube videos in which you feature the content of that community and provide a link in the description.
Write interesting articles on other social media in which you feature content from the community and provide a link to it, where they can find more content.
Occasionally feature a thread on Mastodon or Twitter in which something interesting happened in the community and provide a link.
Answer a common question on sites like Stack Overflow, Quora, or similar with content from your community and link it back to the post the content came from as a reference. People will see your community as a learning resource, if that’s what it is.
Keep pushing meaningful content to the community. It will appear in the “new” threads in kbin/Lemmy and interested people will take a look.
When people comment, interact with them and try to foster more conversation with questions. The more good comments and replies the higher your thread will rank and show in the “active” or “hot” threads. And with that more people will wish to comment and join the conversation, pushing it up even higher if you can keep them engaged.