There’s no sdwdate-server. And unlikely one will materialize. sdwdate (client) is already lacking developer time.
It may not even be easy to run an sdwdate-server inside a VM. Ideally an sdwdate-server would have an atomic clock connected. How? By USB most likely unless there are better options than USB atomic click. TODO research.
Whonix-Gateway CLI has sdwdate (client) installed as all flavors of Whonix.