As to their TRNG, the landing page of official site states that it is based on their patented chip, but I didn't find the relevant patent.
Doesn't really matter, considering they aren't open source:
https://github.com/ngraveio/zero-firmwareAnd given that their secure element and OS are going to remain closed source (
https://support.ngrave.io/hc/en-us/articles/4409555395217-Is-the-ZERO-open-source-), then we will just have to take them at their word. Note that their word includes calling their device "100% offline" and "the coldest wallet", but also involves connecting it to a computer via USB in order to update it.