@solari hmm, I'm not actually sure about the Wordpress plugins. I would have assumed the plugins add the tags automatically. Might need to ask someone more familiar with the two plugins. You're welcome to ask in the indieweb chat! https://indieweb.org/discuss
@pfefferle Still no go -- upon reactivating this plugin and testing at websub.rocks, it reports "Both a self and hub value are required. We didn't find a hub value on your page, but we did find a self. Ensure your page has either HTTP Link headers or HTML or XML <link> tags indicating your hub and self URLs. See Discovery for more information."