The clearest signal of a Learner is curiosity. Curious people, by definition, love to learn. While Experts talk about what they know, the Curious talk about what they don’t know. When you interview, verify expertise by discovering strengths. And then look for Curiosity.
One way to find Doers is to ask a candidate how to do something and then ask them to do it. I ask engineers how they would solve a coding exercise or a sales rep how they would sell cap table software. After listening to the answer I ask them to take out their computer and write code or pretend I am a buyer and sell me software. You can quickly see who prefers doing something versus talking about doing it.