The first and second stimulus payments paid in ADVANCE were safe from child support offsets however if you got the missing payments on the 2020 return as a credit it could be taken.
Once the 2020 return is processed the third stimulus advance payment will be released if you are eligible based off the income on the 2020 return. https://www.cnet.com/personal-finance/your-third-stimulus-check-can-be-seized-heres-what-to-know/
