Indiana doesn't recognize the head of household status like your federal return. Your options are married filing jointly, married filing separately, and single.
If you haven't entered any information for a spouse in the federal part of your TurboTax interview, you'll be considered single for purposes of your Indiana tax return.
If you're married but living apart from your spouse then, according to Married Persons Who Live Apart Filing Status on page 5 of the 2024 IT-40 Income Tax Instruction Booklet found at Current Year Individual Tax Forms:
If you were not divorced or legally separated during the tax year you may have qualified for and filed as ‘head of household’ on your federal income tax return. If you did, do not check the married filing separately box. Also, do not enter either your spouse’s name or Social Security number.