I need to file GA state tax as an individual but filed my federal married-joint.

If your spouse was a non-resident of GA for the entire tax year and had no GA-source income, then you can file your GA return as Married Filing Separately or as Married Filing Jointly.  (You cannot file as Single.)

Georgia requires that you use the same filing status on the Georgia state tax return that was used on the Federal income tax return.

Are you a full year resident, a part-year resident or a nonresident of Georgia?

If you are a nonresident of Georgia, are you completing the state tax return because you have Georgia sourced taxable income? If so, what type of income?

"Georgia requires that you use the same filing status on the Georgia state tax return that was used on the Federal income tax return."

There is an exception when one spouse is a GA resident and the other is not and has no GA-source income..  From page 11 of the 2020 GA tax instruction booklet:

"Exception:

One spouse is a resident and the other is a nonresident without any Georgia-source income, your Georgia return may be filed jointly or separately with each spouse claiming the
appropriate exemptions and deductions."

https://dor.georgia.gov/it-511-individual-income-tax-booklet