Good news for the DPRK air force:
this US Admiral has come to express hypotheses similar to what we have written in the past on this discussion.
I attach a couple of considerations made by hypothesizing what types of aircraft the Russians could provide without the risk of being accused of violating UN sanctions
on July 4th in response to another user I wrote
if there are no upheavals within the UN, numerous sanctions and military embargoes against the DPRK remain active, to which Russia has also officially joined.
This does not mean that Moscow cannot "collaborate" with North Korea to help it strengthen its defense system, but it will do so possibly by trying to disguise supplies/aid with systems that the DPRK already has at its disposal, or with systems also several to which it could potentially acquire also outside Russia.
Therefore
1) In the short term, a significant increase in the number of MiG-29s is possible
either with direct supply of second-hand aircraft from Russian stocks or even in newly produced kits which can then be assembled locally (all old and new with modernization)
2) I don't think that Moscow supplying SU-35 would be too obvious to the whole world, but it doesn't take away from the fact that they could supply deeply modernized SU-27 type SU-27SM/SM2
SU-27 why?:
it was sold or inherited after the collapse of the USSR by numerous nations and made in China as the J-11, therefore an ideal model to make it difficult for others to indicate with certainty who delivered what.
Therefore it seems that this Admiral probably made the same reasoning and that it would be in theory the easiest and least risky way in terms of UN accusations for Moscow to help the DPRK
But the Russians could also provide other types of aircraft and helicopters that they already have in their fleet, such as:
IL-76, Mil-8/17, Mil-26, KA-27 ASW, Mil-24 and if available some SU-25
But also last July it was added
3) In the medium term, contribute to creating a jet trainer with CAS capabilities.
4) In the long term, barring a lifting of UN sanctions or Moscow's open refusal to comply, not the delivery of a possible LTS (Legkiy Takticheskiy Samolyot - Light Tactical Aircraft), but collaboration on the creation of an indigenous North Korean design for a fighter aircraft that could take advantage of what was created for the LTS, but with a slightly different design to be able to claim that it is not an LTS.
This new fighter could be officially built/assembled in the DPRK, with parts produced locally and others that could be supplied by Russia, away from prying eyes.