You have to mail your 2021 return. Don’t forget to sign it.
There is no penalty for filing late if you are due a refund.
If you do owe tax, you should file ASAP to keep penalties and interest from accumulating.
This IRS reference explains the penalties for late filing:
The ONLY way to file your 2021 return is by mail. Expect a six to nine month wait for the IRS to process it.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.