You can read this kb VMware Knowledge Base
There is 2 Web Client ... One vSphere Client (HTML5) and one vSphere Web Client 6.5 (like old web client in older version of vSphere) ...
in the KB you can read :
Will the Legacy C# Client still be available at all?
The Legacy C# Client will still be available with vSphere 6.0 and earlier versions that are not End of Life. For example, the Legacy C# Client will still be available and continue to work with vSphere 5.5 and 6.0. Starting vSphere 6.5 and later, the C# client will not be available.
It means that there is no other client ....