SSH no longer works after update to 10.12.4
no matching host key type found. Their offer: ssh-dss


This error says that the remote server is offering only DSA host key. This is considered weak these days with fixed length of 1024 bits. You should update the server and set up different keys (RSA).

As a workaround, you can use HostKeyAlgorithms +ssh-dss in ~/.ssh/config, which will allow you to connect to this server, exactly as described in the official documentation for legacy algorithms in OpenSSH.