Re: hytera USB packet structure
there's a simple answer. The Hytera-IPSC is proprietary. Unlike the "over the air" interface, which follows a clear specification (ETSI), the network side is not subject to such a specification. In hamradio digital voice we mostly use the homebrew protocol, also called MMDVM. Hytera, whose devices are intended for commercial purposes, use their own protocols. Developers usually only get access to this information mostly after they sign an NDA. Which also means that you cannot and may not publish this information that easily. That's why I have to tell you, your search is unlikely to be successful. You will probably not find what you are specifically looking for.
Hytera-IPSC and MMDVM are similar, but also differ in many places. There are already protocol converters Hytera IPSC <> MMDVM, but only for the Hytera repeaters. However, these were previously closed source. But there is an interesting project: https://github.com/OK-DMR/Hytera_Homebrew_Bridge
73 Heiko, DL1BZ