Is it possible to revoke the Foreign Earned Income Exclusion on TurboTax online? If so, how do I do that? Or do I have to file a hardcopy of my taxes with the statement?

TurboTax does not provide the foreign earned income revocation statement; therefore, you will have to attach the statement to your paper file tax return.

You can simply write: "I hereby revoke my election to claim the foreign earned income exclusion, as authorized by Treasury Regulation § 1.911-7(b)(1). The revocation is effective starting with the taxable year covered by this year's tax return (2018)." 

Please ensure that you include your name and Social Security Number (SSN) on the statement, and sign and date it.