I'm a US citizen & married my wife on K1 visa on Sep 2019. She arrived Aug 2019. She has SSN and work permit; still waiting on green card interview. She has not worked to avoid COVID. Suggestions on how to start tax filing?

You have the option to treat your nonresident spouse as a resident for tax purposes by making the choice described in IRS Publication 519, U.S. Tax Guide for Aliens, designating your spouse as a resident in TurboTax, and attaching a required statement to your mailed (not-efiled) tax return.  If you make this choice, you and your spouse report your world-wide income in 2019 on a joint tax return. 

Otherwise, you will need to file a Married Filing Separately tax return.  Your spouse would not need to file a U.S. nonresident tax return because she did not have U.S. income.

Here is some of the Publication 519 text (click this link) describing the option to treat your nonresident spouse as a U.S. resident for tax purposes:

"If, at the end of your tax year, you are married and one spouse is a U.S. citizen or a resident alien and the other spouse is a nonresident alien, you can choose to treat the nonresident spouse as a U.S. resident. This includes situations in which one spouse is a nonresident alien at the beginning of the tax year, but a resident alien at the end of the year, and the other spouse is a nonresident alien at the end of the year."

To make the choice, attach a statement, signed by both spouses, to your joint return for the first tax year for which the choice applies. It should contain the following information.

• A declaration that one spouse was a nonresident alien and the other spouse a U.S. citizen or resident alien on the last day of your tax year, and that you choose to be treated as U.S. residents for the entire tax year.
• The name, address, and identification number of each spouse. (If one spouse died, include the name and address of the person making the choice for the deceased spouse.)