@gme i didn’t have a Wordpress site back in the day, but I noticed that there were “ping backs” where the comment section of one site cached and previewed a small portion of the comments on a completely different site. Apparently the two webmasters had scripts to crawl each other’s sites. Is that still a thing ?
But wp ping backs is not the same as federating.
That being said there are ActivityPub plugins for WordPress to bring any blog into the federation today.