I want to file 1040xTurboTax says the form isn’t available until 3/25/2021 and won’t let me file until that day. Is there anyway to file through TurboTax before that day

You can print the tax forms on the IRS website and mail in your amended income tax return.

The IRS has not finalized the 1040X form so it can't be e-filed until they approve the form for e-file. This applies to all tax preparation companies, not just TurboTax.

• Once the IRS has finalized the form and the IRS has processed your return, see How to amend (change or correct) a return you already filed?

why are you amending?  certain changes in the tax laws may require filing an amended return but until the IRS publishes the instructions for the proper way to amend   (this would include unemployment compensation, child tax credit, earned income credit) filing before the TurboTax app is updated will likely result in a holdup in the amended return and may even require you to file a correction which could further delay any refund you might have coming.