Hi!

vShere client (C# client that you had to install on windows mahine) has been deprecated as of vsphere 6.5

Currently there are

VMware host client - this is a web client installed on ESXi host

VMware Web client (built on flash) - it's automatically installed on vcenter

VMware vsphere client (aks HTML5 client) - it's also automatically installed on vcenter

You don't need to install anything manually.

You can only upgrade host client separately.