I think the long game is the PRC gets influence with the South Korean government, and makes the deal to agree to unification with the US kicked out of the peninsula, that’s what the PRC really wants.
Yes PRC is the chief suspect here.
The resemblance of the NK missile to Russian missile craft also can point to PRC as they copy/steal designs from everyone and they would want observers thinking there is Russian involvement, taking the eyes off them.
Intel drops have C_A rogue actors and neocons involved in a belligerent NK and leading them with design/tech. It sounds far-fetched to newbies but there’s a ton of credible drops that add up in that direction.