I don't think it's unrealistic at all to specialize in Linux systems in general, but it probably does make it harder to break into the industry vs Windows adminstration.

Cloud/devops roles still require a deep knowledge of Linux to be effective in. Yes, the whole point is that your infrastructure is like cattle and easily replaced, and a lot of the configuration is abstracted away, but when something goes wrong you still need to be able to troubleshoot, pin down the root cause, and correct the issue so it doesn't happen again.

I'm in basically the same position as you, in that I have very little IT job experience, but I think I am quite a bit further along skill-wise from the sound of it. I kid you not, I've been job hunting for over a year now with absolutely dismal success. I'd like to blame the economy, but I get almost no feedback so it could also be that I'm not marketing myself effectively enough.

I'd keep honing your Linux skills, but don't neglect other stuff either. You need devops skills these days, no question. Check out https://roadmap.sh for help knowing what to focus on for a particular path.