You could, conceivably, adopt a fiscal year since you will be filing your first (and also final) 1041 for the estate.
For example, you could adopt a fiscal year that ends on March 31, 2021, which would give you until July 15, 2021 to file your 1041.
Further, although I would not personally recommend it, if you maintain your books in a like manner, you could adopt the accrual method of accounting.
Regardless, the final year deductions (if they result in a net loss) can be passed through to the beneficiaries on their K-1s.
