Does anyone know how to verify a Mastodon profile using a WordPress site?

I would argue... like any other website? The Join Mastodon website has a guide.. For my verification, off of my WordPress install, I just added a link with the rel="me" tag, which led to my green check marks on my Mastodon profile..

Not really sure what you mean? If you mean login using Wordpress as an identity provider, that is not a feature that any lemmy instance provides IIRC.

Are you referring to the verification checkmark? If so, then follow this.