Growth Mindset might be a bit of a wooly term but that tends to be what I look for. I want people who continually get better. There are lots of resources on specific things you can discuss for this. For me, I think simply asking "what was a recent new thing you had to learn" opens up a good conversation.

For ascertaining whether someone meets a technical bar -- the gold standard has to be facilitating some way where they can do some actual work with you. That might be v difficult depending on nature of stack, tech debt, etc. But the closer you can make that sort of process to what would really be happening, the better. Coding exercises really only prove someone is good at coding exercises -- that may or may not have any relevancy to what you do I think.