I also couldn't find a good tutorial, but another commenter here pointed to this blog post: https://blog.joinmastodon.org/2018/06/how-to-implement-a-basic-activ

I also couldn't find a good tutorial, but another commenter here pointed to this blog post: https://blog.joinmastodon.org/2018/06/how-to-implement-a-basic-activitypub-server/ https://blog.joinmastodon.org/2018/06/how-to-implement-a-bas... Maybe it's a good starting point?