For the MAC, the article suggests an exception to github.com. But it looks like an exception is required for the Kex protocol as well. I see this error:

   Unable to negotiate a key exchange method

If I understand correctly the response from ssh -v -v, github.com only supports the following Kex protocols:

ssh-rsa-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-rsa,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-dss-cert-v00@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-dss

Edit: By trial and error, I find that this works for github.com:

KexAlgorithms diffie-hellman-group1-sha1