How to file an amended tax return for 2021?

Do not amend unless your original 2021 return has been fully processed.

And....your amended 2021 return has to be mailed....it cannot be e-filed.

https://ttlc.intuit.com/community/tax-return/help/how-do-i-amend-my-2021-return/00/2544441

Only certain paid tax pros can still e-file past year amended returns. You cannot e-file an amended return that you prepared yourself using TurboTax.  Your 1040X must be printed, signed and dated in ink, and then you need to mail it in.  Use a mailing service like certified mail so you will know the IRS received it, since you will have a long wait for it to be processed.

Even during “normal” times it takes about four months for the IRS to process an amended return.  During the pandemic and due to the severe backlog at the IRS it is taking much longer—six to nine  months or more for many amended returns.  Do not expect quick results from amending.  When the IRS issues a refund for an amended return it will be by check.  They do not make direct deposits for refunds for amended returns.  You can watch for information here:

https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1