Ask HN: Minimal ActivityPub Server?

I want to join the fediverse by opening a small postbox of my own that I can use to interact with other instances (Mastodon, Gnusocial, etc.) on my own terms.

I have a domain I can use, an RPi4 I already use to host my website, I now wish to host a small activity pub...

... how do I do this? I was expecting that simply searching on github or gitlab would yield ready to deploy lightweight projects, given how small and simple the whole protocol is. Instead I've found docker scripts to run full webstacks.

If IPFS (infinitely more complicated protocol) has a pure JS implementation that can be run entirely in a browser addon, how does a relatively small protocol like Activity Pub not have tiny implementations too?