Since XenApp and XenDesktop 7.9 and StoreFront 3.6, it is possible to use SAML authentication with a number of external identity providers and integrate that with the Citrix Federated Authentication Service so that users can be authenticated from NetScaler through to StoreFront.
Integrating reCAPTCHA by Google with Citrix NetScaler is a great move towards protecting internal resources from attackers. If someone or even a bot of computers are trying to brute force an account, or break in to your system, having reCAPTCHA is sure to defer such activies and make it a very difficult task to achieve.
When it comes to Skype for Business with XenApp or XenDesktop, your first action will be to optimize the delivery of audio and video calls using the Skype for Business Optimization Pack. In some cases, the Skype for Business Optimization Pack will not suit so it is equally important you have the correct or best possible fallback procedures in-place to support such users.