Kindlets have been essentially unsupported since FW 5.5.x, so, you're in for a world of pain. Booklets, on the other hand, are supported, but the API is private, and now has key bits of it obfuscated...
c.f., the hoop-jumping involved to get KUAL running almost everywhere...

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EDIT: As I can't remember whether that's specified somewhere in the docs, the repo of the mangled Booklet variant for current FWs is here:
https://github.com/NiLuJe/KUAL_Booklet (it links to the main repo, so you get everything).