Do you mean do not show any notes from Mastodon?
Discussion
I think blocking notes with nostr addresses from some domain.
nostr:npub108pv4cg5ag52nq082kd5leu9ffrn2gdg6g4xdwatn73y36uzplmq9uyev6 is it possible to specify mastodon domains on nostr more fine grained than mostr.pub?
Yes.