It will be hard, most Hong kongers lack the linguistic ability, ie mandarin and simplified chinese, to work in the mainland. There is also plenty of talent that is equal or better that companies can pay less for in the mainland, so why bother.
Actually linguistic isn't a problem for internships or working in mainland as many people in Shenzhen and Guangdong can speak or at least understand Cantonese. Many retired HKers live in Shenzhen or Guangdong nowsaday. Although living or working in China doesn't mean these HKers would be less brainwashed. The problem in HK right now is the education and media. Many kids and teenagers were brainwashed when they attended kindergarten, elementary, and high schools. By the time they attended colleges or worked, it is too late.
In the end of the day, the problem in HK is that the ruling elites are mostly bureaucrats not politicians. That's why HK politicians are cowards. Many people have warned the HK government that there are fundamental problems in HK education but nothing was done not even now. Carrie Lam is weak and gutless. The only thing she has done is hidden behind the HKPF. She doesn't dare to confront the schools that allowed students to participate in the protests or the media which is obvious bias or the judges who made rulings that are absurd.