If you were still legally married on 12/31/2023 then you can only file as Married Filing Jointly or Married Filing Separately on the 2023 tax return.
It depends. If you are not divorced by December 31, 2023, you have the option of filing married filing jointly (usually best), or married filing separately. You can create two accounts to see which is best, then decide what you how to file.
Depending on your circumstances you may be eligible to be considered unmarried in special circumstances. IRS Publication 504
To be considered unmarried at the end of a tax year, your spouse may not be a member of your household during the last 6 months of the tax year and you must meet other requirements.
1. You file a separate return. A separate return includes a return claiming married filing separately, single, or head of household filing status.
2. You paid more than half the cost of keeping up your home for the tax year.
3. Your home was the main home of your child, stepchild, or foster child for more than half the year. (See Home of qualifying person, later, for rules applying to a child's birth, death, or temporary absence during the year.)
4. You must be able to claim the child as a dependent.