I did manage to get a list of all users without a verified email using a postgress command, but sadly no, I can not figure out how to use the PurgePerson or AdminPurgePerson endpoints that are "described" in the documentation. I ended up just writing a small python script to ban all of them for now until I can figure out how to purge them.
It's extra tough because user management in Lemmy is tied to posts and comments right now. Since none of the spam accounts have made posts, there's no way in the UI to purge their accounts.
You must not use the code of codes!