A weaponized strain would be designed deliberately to be indistinguishable from a natural origin, so there will be no proving that without documents or a confession. An incidental genesis would be an intentional chimera, produced just for research, that got loose. An accidental genesis would be very like a natural origin, but just in lab animals based on strains handled in the lab, maybe even mixed with a natural strain brought in by accident, even incubated unbeknownst in a lab employee.
Personally, I doubt we will ever know more than we do now. All four are possible, all four should be guarded against in the future. But guarding against weaponized viruses is arbitrarily hard. Russia probably still has casks of weaponized smallpox stored underground somewhere. US and China, too, possibly.