I've written an ActivityPub server which only allows you to post messages to your followers. That's all it does. It won't record favourites or reposts. There's no support for following other accounts or receiving replies. It cannot delete or update posts nor can it verify signatures. It doesn't have a database or any storage beyond flat files.
But it will happily send messages and allow itself to be followed. This shows that it is totally possible to broadcast fully-featured ActivityPub messages to the Fediverse with minimal coding skills and modest resources.

They say, it doesn't matter which Mastodon instance you sign up with. You can still communicate with the entire Fediverse and when push comes to shove, you can also always move. Well, push came to shove for me and I had to move. So let's talk about the giant asterisk that belongs after both of those claims.

Hugo based static page generator and blog with ActivityPub support

A curated list of server applications with support for the ActivityPub protocol (Fediverse network) and related standards.

Tag-indexed bookmarking, ActivityPub publishing (soon to be optional!) and simple commenting, also powered by ActivityPub (also optional)

Spawn a Nginx webserver with a bunch of static JSON files that behaves like a Mastodon instance

This program runs as a daemon (proxied by a TLS-enabled real httpd server) and provides the basic services for a Fediverse / ActivityPub instance (sharing messages and stuff from/to other systems like Mastodon, Pleroma, Friendica, etc.).