Most corporations and bigger companies will probably make you use Windows, so knowing a little about how to use it might not be bad. But do not try to blame the OS for your mentioned problems. You can program all mentioned languages on Linux, so I really do not see how Linux could be your problem in any way.
Also, if you are able to program in a few languages, learning a new one for a job is a matter learning a few principles in a few days to get you up and programming. Your code might not always look good or be performant, but duh, you are 21 years old, no one expects you to be a senior developer with deep specialization!
You say that many companies search for Java developers, and it seems to be your favorite language (as you mentioned it first). So why not try to apply for a job which requires Java. Good Java will not even care about the OS, as the JVM takes all the difficult differentiation away for you, so you might even just stay on Linux and not miss a thing at work!
By the way, learning new technologies and languages is a good thing and you should do it! Learing helps you become a better developer. I am currently learning Rust. It is so very difficult, because it is different. But I love it! So what will you learn next?