I used to do my interviews in C++, but then I got burned during a Google interview when my interviewer talked about the inefficiencies of emplace_back vs push_back (I had no idea). After that point, I just decided to do JS because I was reasonably proficient at it, and it is actually faster to write than C++ in a lot of cases (less boilerplate).
The top LeetCode answers / YouTube explanations and such are usually in Java or Python, so sometimes it's also hard to find a good JS answer. I'm leaning towards Python, because it is more like JS and with less boiler-plate like Java, but I'm worried about something throwing out some random trivia about Python that I have no idea about, because honestly I haven't used it much in my career thus far.
From most important to least important, here are the criteria I'd consider wrt to language choice:
The above criteria is true for almost all Big Tech jobs. Interviewers here are trained to be language agnostic since the company uses dozens of technologies. (If you interview at a consulting shop, they'll likely be much more strict about what they want. These companies also pay significantly less.)
Going into the issue further, here's the breakdown I've seen:
If you're more interested in what the other side looks like, we actually gave a masterclass about it (heavily inspired by my experience back at Meta). You can watch it here: [Masterclass] How To Be An Amazing Interviewer In Tech
I'd say if you have a domain specific interviews like for Android/iOS or FrontEnd the choice of your language does play a role. For Android the interviewers would expect you to write code in Java and Kotlin. When I interviewed at Expedia I was asked to code in Kotlin as that's the official language for Android development.