I have setup the VPN service within my Fritzbox 6660 cable modem. I can connect using windows, iphone or any android smartphone. Just setup the VPN settings and GO!
But a big bummer as it seems Android TV still does not have VPN settings in the network settings.

So you need to install an app to be able to use VPN but all apps offer their own VPN service but I need to connect to my own VPN server that has been setup on the fritzbox 6660 cable modem and that uses an Android VPN client being able to connect to a "IPSec" or "IPSec Xauth PSK" VPN server.

So I have these settings:

VPN type: "IPSec" or "IPSec Xauth PSK"
Server address / Server: *****
IPSec ID / Group name: *****
IPSec key / Shared secret: *****
username / Account: ******
Password: *******

Which VPN client/setting do I need to connect to this VPN server/service using Android TV on a Google with TV Chromecast or any other Android TV STB/SmartTV ?