Who decides?
The municipality. Eligibility is assessed case by case and may involve an investigation into your actual living situation.
Briefadres
A correspondence address is a formal municipal solution, not an informal workaround.
A briefadres may be available when you have no residential address. The municipality assesses the circumstances, verifies the address and normally requires written permission from the person registered there.
What is normally needed?
Identity documents, an explanation of why you have no residential address, supporting evidence and written consent from the correspondence-address provider.
Municipal support
Where no private correspondence address is available, ask whether the municipality can provide or arrange one under the applicable rules.