In reply to Alan Levine.

I've been having some issues with it for the past week or so, likely as the result of the upgrade to Mastodon 4.0 and the increases in traffic, but the best/only method for syndicating from my site into a separate Mastodon instance that also includes alt-text for photos is Brid.gy (see: https://brid.gy/about#picture). If set up in conjunction with Webmention plugin (and optionally the Semantic Linkbacks plugin), Brid.gy will also feed back replies/likes/boosts from Mastodon back to your website as comments. If you do use Brid.gy to syndicate/publish into Mastodon, you're going to want some basic proper microformats support for your theme. I'm happy to help describe this in a crash course if you don't have the expertise on microformats, though I know you've got the theming background to pull it off. (See also: https://indieweb.org/WordPress/Themes#Microformats)

Two other options here are:
* to use https://fed.brid.gy/ which will go a long way towards making your WordPress site look like an ActivityPub/Fediverse instance, or
* use Matthias Pfefferle's ActivityPub, Webfinger, and NodeInfo plugins which will give you a lot of the same functionality (this is what I've opted for making my whole site followable as @chrisaldrich@boffosocko.com). This option also automatically adds alt-text to photos if they have them in your own website.

I haven't compared the two options in over 18 months, but I think Pfefferle's may give stronger/broader support presently. The thing these don't give you is a reader interface for subscribing/reading/direct interactions, but that can be done reasonably with a feed reader, or even better with a social reader. I've outlined some of this functionality in the past: https://boffosocko.com/2021/04/26/a-twitter-of-our-own-at-oerxdomains-2021-conference/