From what I've read (http://www.gremwell.com/ssh-mitm-public-key-authentication), if you use public key authentication with SSH, the MITM will break the authentication (forcing ssh to ask for a password). It's the same as with TLS client certificate authentication: in the same way the server certificate authenticates the server to your browser, the client certificate authenticates your browser to the server, and the server will reject MITM connections as unauthenticated.

While unfortunately for TLS client certificates are not a solution against MITM due to their awful user experience and privacy concerns, for SSH public key authentication has a good user experience, and is very common.