Replace ProxyJump in ~/.ssh/config

ProxyJump was added in OpenSSH 7.3 but is nothing more than a shorthand for using ProxyCommand, as in:

Host hidden-host
  ProxyCommand ssh proxy-host -W %h:%p

If your ssh version is even older, you might lack the -W option, in which case you can use nc, as in:

Host hidden-host
  ProxyCommand ssh proxy-host nc %h %p 2> /dev/null

Related