I have done some research on this topic and found the following. I am not giving any tax advice, but just sharing my findings:
According to IRS Guideline on Recovery Rebate Credit , you are not eligible for the Recovery Rebate Credit if you may be claimed as a dependent on your parents' 2020 return. The key word is "may". It does not matter whether your parents actually claimed you as a dependent or not. It all falls under the definition of a "dependent".
In your case, "dependent" means a Qualifying Child per IRS definition? Were you under age 24 at the end of year? Did you provide more than half of the support you need for the year? If you did provide more than half of the support in 2020 (i.e. passing the Support Test), then you may be able to claim the credit.
