The Funkwhale music platform is alive and in active development, and they’re working on a feature to filter far-right artists off the network. Some Fediverse self-hosters are divided on letting a third party decide what should be allowed in their library.
Technically, SoapBox and Rebased were forks of the Mastodon frontend and Pleroma backend by an alt-right dev that found some level of success in the alt-right part of the Fediverse. So, it’s not completely unheard of.