Divorced but was married last year. I don’t have my ex wife’s ssn and have zero contact with her. Can I still file without her ssn?

You could file as Married Filing Separately without her SSN. This return can't be e-filed and will have to be printed and mailed . Simply write NRA where her social security number would go before mailing. Attach a statement to explain your situation.

If you meet the qualification to be "considered unmarried" you might be able to file as Head of household.

To be Considered Unmarried:

1. You file a separate return

2. You paid more than half the cost of keeping up your home for the tax year.

3. Your spouse did not live in your home during the last 6 months of the tax year. Your

spouse is considered to live in your home even if he or she is temporarily absent due to special circumstances.

4. Your home was the main home of your child, stepchild, or foster child for more than half the year.

5. You must be able to claim an exemption for the child.

if you weren't married at year-end 12/31/2021, your filing status is single or head of household. do not select divorced since there isn't such a filing status for federal

if you  were married at year-end, your choices are joint, married filing separate (spouses SSN required) or if you live apart for the last 6 months and had a  qualifying dependent you could file as head of household (spouse's SSN not required)