How can I get my manager to dig more into the "awkward" stuff in 1 on 1s?

Are you wanting to build the relationship gradually so you have the trust and rapport such that you’re getting these details organically, or are you fine doing that over time but you want actionable feedback right now?

The long game of building trust will be maintaining confidence when trusted with information, keeping your word, being transparent yourself, and seeking stretch goals. You don’t have to always achieve stretch goals, but seeing self-initiation is helpful.

If it’s “cut to the chase” feedback: “I prefer a very direct communication style, I struggle to read between the lines. Even if you think some feedback is too forward or rude, I really do prefer to hear it unfiltered and make a plan to improve”

“I am in a growth phase, and can’t grow without clear feedback. Can you give me one thing I am not doing or could do better to focus on between now and one next meeting?”

“We have talked generally about my work, and I am interested in very pointed feedback to improve. If you don’t have detailed feedback, could you ask person X and Y who I have worked with directly. If they are comfortable they can tell me directly, otherwise please synthesize it and deliver it yourself.”

You need to be clear with your needs. If their boundaries are “I don’t give feedback outside of formal reviews” they are a bad manager, but I doubt that’s the case. They are getting their bearings still, but if you are very direct with your needs hopefully they can hear it.