Only Let Specific Users Review PRs? / Prevent random reviews?

How can I only allow PR reviews from specific users?

Or more specifically, only allow PR reviews from those with repo access or who have contributed to the repo?

My team just got an approval from this user: dj110919871 · GitHub
This user’s account is only 15 days old and they reviewed 26 PRs in 1 day.
It’s either someone who is trying to look like they’re doing something or some kind of weird spam/bot.

So how can I prevent these unknown/random/spam users from reviewing PRs or leaving comments or anything?

Also, I know that only reviewers with write access count for approvals, but still, it’s annoying, so I’d like to prevent it.

You can use this (it’s incredibly awkward):
https://docs.github.com/en/communities/moderating-comments-and-conversations/limiting-interactions-in-your-repository

Otherwise, you can report accounts (which shouldn’t be your job).

Beyond that, I’d suggest contacting:
https://support.github.com