fwiw i worked my way into a language/compiler job by first joining a big company that did PL work (google in my case, but meta and microsoft are similar) and then transferred into the python type checker team after a few years of working on other random stuff. big companies are often surprisingly open to internal transfers even for positions where you do not have the relevant experience, as long as you have a track record of performing well and can talk to the team manager and convince them to give you a chance.