After endless attempts, it turns out that the whole problem was in the plugin itself, and the plugin itself was written for me by ChatGPT, and I can now say with certainty after endless attempts - he can't write plugins at all!
@MastodonHey @dave, with #WordPress, @activitypub.blog and #PostFormats activated, you can also write long-term (WP standard) posts and asides (or create quote, image, video content).
