You should file jointly for 2019 for the best tax advantage. When entering your spouse's information in the My Info section one of the screens will have a checkbox for "This tax filer passed away in 2019". Make sure you select that checkbox.
Now depending on serveral factors, you may not be able to e-file the tax return. If the entity handling the final arrangements (usually the funeral home) did their job, they notified the Social Security Administration of their passing. The IRS pulls taxpayer information from the Social Security Administration around Dec/Jan every year. That's how the IRS gets notified of someone's passing.
When the IRS is aware of someone's passing, they lock the social security number so that it can't be used fraudulently. While there are numerous errors this can generate when you attempt to e-file a tax return with that SSN on it, the most common error is "SSN LOCKED".
So if you get that error when attempting to e-file, you have no choice but to print, sign and mail the return to the IRS. There is absolutely no work around either, by intent and design.
If you have qualifying dependent children, you may also qualify to file your 2020 tax return with a filing status of "windowed", which will give you a higher standard deduction.
