I don't have a source for you, but I know from everything I've heard that all 'professions' will be available to every tribe. This isn't your traditional MMO where only certain races get to use certain abilities. CoE sets itself apart by being a game where you can do whatever you dream, even if it is sub-optimal.
I believe that was the point of the listed professions for each tribe. Those are what the tribes EXCEL at, but aren't exclusively limited to. And depending on what you choose, it could be very difficult.
For example, I'm sure you can play as a Dras, and try and be an animal trainer. But there may not be many trainable animals in the swap, so it might be very slow and difficult. Similarly, if you want to be a Hrothi carpenter, I'm sure you can, but you're going to have a very hard time getting lumber down into your home in the mines, and working on it. The listed professions are the most commonly found for those tribes, because of the natural resources available around them. But by all means, break the norm! Set up trade routes to get the resources you need into the biome you're in!