Hacker News Reader

Here's a list of developer tools that might be helpful:

https://codeberg.org/fediverse/delightful-activitypub-develo...

I haven't, but the way I'd do it would be to use something like this: https://github.com/edsu/feediverse which till turn your RSS feed into Mastodon toots.

If you want to use Mastodon for comments, there are a bunch of blogs written about integrating them into a comment section (for example: https://zerokspot.com/weblog/2021/01/07/comments-via-mastodo...)

There is a plugin for wordpress that exposes a blog to the fediverse.

ActivityPub Overview