What are some interview red flags you should not take a job offer?

None, apply all you like - less than 1% get offered a job. Nothing they told you during the interview is related to what you shall be working on.

It's hard to tell. During an interview the interviewer plays their "A Game" with a fake smile

I do not know. Interviewers can be deceptive

A job with no job description nor clear terms

At the end of the interview I usually ask how long was the previous person, and why he/she left. If the person was there just 6 months to a year, it may reveal a high-stress or difficult work environment.

Negative tone/attitude of the interviewer Non work related questions that are personal or about children

If work culture is not matching as you need. Then don't join. Money is not the complete package.