In nos.social we look at user look up / search and if it looks like a fediverse address we find the nip-05 from mostr and let users follow the fediverse account. It is under documented but works well. 

https://github.com/planetary-social/nos/blob/a1d75348703851e4f5a51ca3ac21c26ef61882e3/Nos/Service/RelayService.swift#L734 

 Is it possible to surface fediverse accounts in nostr onboarding?