I have dual British-EU citizenship, so cannot apply for settled status. Am I covered by the Withdrawal Agreement as a dual national?

If you exercised free movement rights before naturalising as a British citizen, then you are covered by the Withdrawal Agreement. You will have family reunion rights and rights under social security coordination.

However if you never exercised free movement rights - for example you were born in the UK with both your British and your EU nationality, then you are not covered by the Withdrawal Agreement.

Helpful documents to explain this: European Commission Guidance Note, European Commission Q&A, UK Government guidance on social security coordination.