At this point I can't think of any. 4.4 for
Onyx Book has been teased, but AFAIK isn't officially available and no idea when/if it will.
There is a pre-release version of 4.4 for some models here...
http://ereader-store.de/en/content/8-downloads
...discussed here...
https://www.mobileread.com/forums/sh...d.php?t=286107
https://the-digital-reader.com/2017/...onyx-ereaders/