After seeing a Mastodon post with embedded links, I fell down the rabbit hole of trying to figure out how to actually post HTML to Mastodon. As far as I can tell, Mastodon will accept HTML posts from other ActivityPub servers, sanitize them and display them correctly. But even though the API examples show statuses with HTML content, actually calling the API that way just creates a plain text post. So if I want to republish fleets with HTML to Mastodon, I'll have to run my own ActivityPub server.