You can see their bios on signalfoundation.org , but it doesn't look very promising at a glance. Think tanks, federal agencies, NGO blob, etc.
But to be fair that's the person in charge of policy, so it's the kind of profile you'd expect. (Of course, you're free to argue that a messaging application has no good reason to hire for such a position in the first place.)
Let's be fair: there's a big difference between "this person has worked in or near the federal government" and "this person has literally committed war crimes".
If there are specific concerns about the people on Signal's board, I'd be interested in hearing it, but having Fed connections doesn't inherently mean a whole lot.
This announcement shows clearly that Signal is at the end of its life and it is time to jump ship.