tl;dr: I'm a dev, I work for a good company, but I want to grow in technology X and this company doesn't care about that technology nor does it have the opportunities I need. I believe I need to go to another company. How do I assess whether the new company will give me the opportunities I need?
I'm a software developer and I've been at my current company for about 6 months. The thing I'm having trouble with is advancing my career. Recently, out of my own initiative, I've designed a very rough career plan for myself and discussed it with my manager, but while he seemed very receptive, the opportunities just don't seem to be there.
When I joined I was an expert in technology X, and I really want to continue down that path. I wasn't hired because of that particular technology, nor was I ever explicitly promised I would work with it (I should have asked more questions about this before joining), but I was under the assumption that I would get some decent experience, since it's a technology that's used in many software applications and I'm by far the most knowledgeable person in the company on that technology.
I would really like to keep growing in that technology, but this company doesn't seem to care at all about this technology, which I deduce from the facts that since I joined I haven't touched that technology at all (they heavily favor one of the competitors, something they didn't tell me before I joined), they have never provided any training support on that technology, nor any support for a conference on that technology that I attended recently (not even giving me the day off, I had to use my PTO).
I am convinced that my priorities and my company's are different and I need to find a new company (though I accept frame challenges on that). What I want to ask is how to better approach this in the interviews, how to better assess the role that I will have on a company and whether it will help me grow in the direction in which I want to grow (which is slightly more complicated than just using technology X). Can I present a career path on an interview? Who do I speak about this, how do I speak about it, and how do I gauge their answers?