Go with people who are willing to use their real name, a lot of times it'll be in the channel description, or sometimes in a channel trailer or intro video. Sometimes in an interview some other outlet/creator has done on the content creator. Then google that real name and check their work history and education credentials. You can usually find a LinkedIn. If they're a proper academic, their university will usually have a brief page on them on the official university website. If they're an alumni, they can sometimes be found in an alumni list, various class lists, or publicly accessible projects they worked on, though not always. Work history often cannot be as easily verified, but sometimes can be if you dig a little. Depends on field.

It's not too different from what you'd do if you wanted to hire someone to work for you in a small business or something.

Once you have a significant knowledge base yourself, you can start to use the sniff test, though that's always far from perfect. Less time consuming though.