I self host FreshRSS and among the many sites I subscribe to, I also subscribe to quite a few hashtags on Mastodon which I’m aware isn’t highly publicised so not everyone knows you can do that.

If someone reads this comment that didn’t know you could do that -

Instance/tags/hashtag.rss

Eg:

https://mastodon.social/tags/introduction.rss

You are welcome.

(Set your purge limits aggressively, because despite people suggesting otherwise, you will very quickly have thousands of unread articles to trawl through)