When server requires ssh-dss host key algorithm it is not possible to configure sFTP camel component to use such key type, therefore connecting fails with "com.jcraft.jsch.JSchException: Algorithm negotiation fail".
When these two properties are added in debug mode:
in SftpOperations class:
the connection is established successfully.
It should be possible to configure "server_host_key" and "PubkeyAcceptedAlgorithms" in camel sFTP component.