I think thatās just other peopleās feeds. Not your Nip-51 lists.
Discussion
Content moderation is implemented by filtering the feed with mute lists as defined in NIP-51. You can subscribe to other people's lists as well.
As for filtering by hashtags, you can do a query search (#hashtag OR #another_hashtag OR ...) and save it as a feed.
Check out the query syntax here: https://www.sqlite.org/fts5.html#full_text_query_syntax