Function unknown_route 

pub(crate) fn unknown_route(uri: &Uri) -> Response

The answer for a path nothing serves, and for an XRPC call nothing proxies; see crate::proxy::fallback.

MethodNotImplemented under /xrpc/, which is the name atproto’s XRPC layer uses for a procedure a server does not implement, and a 501 to go with it: a client that asked for a method this server does not serve should learn that this server has not built it, not that the URL was a typo. Anything outside /xrpc/ is an ordinary 404.