You cannot e-file the request for an extension but you can still mail it in to the IRS.   An extension only gives you extra time to prepare and file your Form 1040---it does not give you extra time to pay your 2020 tax due.

https://www.irs.gov/pub/irs-pdf/f4868.pdf

The extension request can only be printed and mailed, as required by the IRS.  The extension request is only for filing the tax return on or before October 15, 2021.  It does not extend the time to pay any federal taxes owed.  They have to be paid by June 15, 2021 to avoid any failure to pay penalty.

Taxes owed can be paid on the IRS payment website for Direct Pay - https://www.irs.gov/payments

Go to this IRS website for the extension request - https://www.irs.gov/forms-pubs/extension-of-time-to-file-your-tax-return

Victims in FEMA Disaster Areas: Mail Your Request for an Extension of Time to File

To request an extension to file your federal taxes after May 17, 2021, print and mail Form 4868, Application for Automatic Extension of Time To File U.S. Individual Income Tax Return.  We can’t process extension requests filed electronically after May 17, 2021.

Find out where to mail your form.