This update was posted yesterday by IRS on their "Operations" page.  I haven't seen it mentioned elsewhere.

E-filing your 2020 tax return: To e-file you will need to enter your AGI from your tax year 2019 tax return. If your 2019 return has not yet been processed, you may enter $ 0 (zero) as your prior year Adjusted Gross Income. If you used the Non-Filers: Enter Payment Info Here tool last year to register for an Economic Impact Payment, enter “$1” as your prior year AGI.

https://www.irs.gov/newsroom/irs-operations-during-covid-19-mission-critical-functions-continue