No. You don’t have to be paid through an umbrella PAYE solution, but if you are permanently IR35 captured it may be your best solution.
Following the IR35 changes in the private sector from April 2021, the responsibility for determining whether contractors are IR35 captured or not sits with end hirer.
If you receive a status determination statement advising you that you are captured, you may need to revise the way you operate in order to remain PAYE compliant for HMRC. If you are permanently captured by IR35, and the agency or end hirer closest to you in the chain does not operate a payroll function, becoming an employee of an umbrella company will allow you to get paid via PAYE whilst remaining as independent as possible.