And people always suspect Russian assistance to *North* Korean missile developments... I feel that for the past 20 years or so, the Russians have been doing (albeit very quietly) far too brisk an arms trade with the South to even contemplate that!
Everybody was quick to note how the KN-23 TBM is a dead-ringer for the Iskander-M, but few were prepared to admit the Ukrainian Grom is plenty similar enough too. Or that the KN-19 resembled the SS-N-25, when the likeness to the (also Ukrainian) R-360 Neptun is in fact closer (length, engine config, booster exhaust). And nobody has offered a consistent explanation of how the ATACMS-copy KN-24 fits into this framing - do we seriously expect the US to have lent a hand here?
I'm not necessarily even accusing Ukraine of actively abetting NK, given its proclivity for hacking attacks & clandestine ops there are numerous other ways for the technology to end up in its hands. The point is that considering the intersection of both ready availability of alternative sources of inspiration and manifold Russian involvement in SK defence projects, deliberate aid to the North by Russia seems decidedly unlikely.
Without even counting the early (mostly pre-2000), fairly obscure direct sales - such as T-80U, BMP-3, Ka-32, Ansat, Il-103, Murena - there is plenty of cooperation. Take KM-SAM (which is basically to S-350 Morfey what the L-15 is to the Yak-130) and now we have an apparent Yakhont-clone. Hell, you may legitimately wonder about the Hyunmoo-series of ballistic/cruise missiles, while we're at it. The H-II is itself hardly a million miles removed from Iskander-M, and there are definite similarities between Kalibr/Iskander-K and H-III! I mean, the very fact that both families subsume ballistic and subsonic air-breathing missiles under the same designation seems a conspicuous parallel in and of itself.
I think it's time to cut the Russians some slack and look elsewhere for the culprit in supporting the North!