"You have until the due date of your 2020 return, May 17, 2021,"
this is generally true , but in your specific case, since you already e-Filed, you have until Oct 15.
Most people don't know this. I didn't. that's why I said use form 4868 initially.
Is there anything else ?
If you don't accept this analysis, refer to some other thread for the answer.
