You don’t need CrystalHD to watch some content, so it still has some use for people, but I do agree that AppleTV is dead now (we will end the support soon).
We had CrystalHD support for Kodi v16 (Jarvis) and those images are still available on our website. But it wasn’t possible to get the card to work well on Kodi v17. As there are few users and the platform is quite old, it’s better to focus our efforts elsewhere.
As for the USB issue: did you try another USB?