@jakimo: Both the framework & the webkit stuff should handle OTF (TT or CFF) (mostly) properly, especially with a custom FreeType lib.
It's a bit dumber than on FW 5.x, though, so you will have to *rename* them to .ttf.
(The only thing that might cause trouble is TT/OpenType *collections* file, and, even then, YMMV).
The usual warnings still apply, playing with fonts on a Kindle has always been and still is a fun way to potentially trigger a framework temper tantrum

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