Is Java and a few supporting skills enough for a junior backend job in Quebec?

Java plus the supporting stack you listed can absolutely be enough to get your foot in the door. For a junior role, nobody expects you to know CI/CD or cloud platforms inside out; they mainly want solid Java fundamentals, enough practical experience to avoid careless production mistakes, and a willingness to learn. With three years available, focus first on writing lots of Java and understanding core concepts, then gradually add SQL, Docker, AWS, and deployment practices. Trying to learn everything simultaneously can become overwhelming.

Java is a perfectly viable primary language, and plenty of backend developers work mostly with it. You should also build a foundation in databases, Linux, networking, operating-system basics, and language-independent programming concepts. You don't need to master every tool before applying—companies generally expect junior developers to learn their specific systems on the job.