Well, you can't trust _any_ device if that's your line of thinking. Not an iPhone, not an Ubuntu phone, no device whatsoever. Not unless you've baked your own chips, or made some contraption running your software in parallel on different CPU architectures.

If you're going to do anything, including working on the computer you're typing your comments on, you have to trust a lot of parties. Some of that trust involves knowing who made the code, and some of it may involve the knowledge that the NSA will not be using their best, most secret backdoors against a whole lot of people.