1) Contact Citrix support about some missing details in their SDK (Dynamic Virtual Channels were not loading properly on XenDesktop, and the SDK docs just said "Use the Microsoft APIs for registration")
2) Citrix ponders about the issue for a few months. I write a full DVC plugin for them to test things with, because they don't seem to have anyone in-house who knows their own tech stack
3) Citrix finally declares that dynamic virtual channels are currently broken. They might get fixed in a future release, but they're not on the active roadmap.
4) Citrix is still releasing frequent updates to the SDK, advertising DVC support. NB this is not just a small typo in the docs, they have a long chapter dedicated to the topic ( Citrix Dynamic Virtual Channel Protocol at https://github.com/citrix/receiver-for-windows-virtual-chann... ). The feature is very thoroughly documented, it's just...not actually implemented.
I can't imagine how many developer hours get wasted yearly with people trying to get virtual channels to work, when in reality they're just flat-out not supported.