from their about page, "Metalhead.club is a Mastodon instance hosted in Germany and powered by 100% green energy. Mastodon is a free and decentralized alternative to well-established social microblogging platforms like Twitter. This instance is especially addressing Metal fans, but can be used by anyone else as well ;-)"
green metal? yeah, we got that.
This is a private instance that @firstname.lastname@example.org is using for development and testing.