This is sort of deflection from you since focus is on military section of DPRK and not overall for which even then is inaccurate in way you generalize them.
DPRK over a
ago was suspected of being effectively able to produce domestically complex/advanced machinery thus negating impact of sanctions.
"effectively able to produce domestically complex/advanced machinery thus negating impact of sanctions" is a very broad statement.
Yes, DPRK does produce, and produce a lot - especially for country of ~26 million (around/upto 5 million in mil-related industry). This statement doesn't reflect either nomenclature or the exact level of what this "advancedness" means.
F-16 is an "advanced fighter"(depending on source - it can be 2020s V or 1980s C), regardless of existence of F-35. And this statement is generally true - producing F-16 requires a very high level of industry, which few countries can boast. Yet F-16C isn't F-35.
Yes, North Korea can produce a lot of advanced equipment - and yet it's whole chain, everywhere from material science(and application) for the most boring screw and sheet metal, is often not there where Russian one is. Essentially
everything, military or not, that is produced in DPRK, can be vastly improved by applying Ru- know-how; if there are specific items, which DPRK produces better than Russia - it isn't because of DPRK being more advanced in a specific field(there are literally none such fields), but because Korean engineers and administrators are quicker-witted at exploring new ways of using available technology(which happens a lot with Russia, to be fair - and it's paying a huge price for long-outdated schauvinism) . But with all that said - ultimately a comparison between two industrial countries - small and poor(er) and big and rich(er). Even Russian capability to obtain foreign-sourced(western) components, manufacturing equipment, etc is at a scale fundamentally not available to DPRK.
DPRK being industrial country at this economic level is by itself a huge achievement - but let's measure.
Current opportunity for DPRK, when, due to an unexpected combination of extreme Russian need, (North)Korean capability to provide exactly what is needed, in huge numbers, and South Korea's lack of foresight (remarkably - only the last part was the truly decisive one) - is a historic opportunity not to be skipped, and it can be expected for them to use it as such.
Btw, given that most probably Russia pays for DPRK solutions in hard cash(in huge volumes for the scale of North Korean export economy) -
procuring Chinese industrial solutions at a scale is now possible, too.
Yes, those that China will agree to sell - but for an economy in need of everything, they will not run out of options where to spend the money.
Chinese equipment is not available to them regardless of financial situation and is similar situation to western hardware and was with Russian until very recently.
Chinese civilian/manufacturing equipment
is available to them -
if paid for (sad rule number 1 of having business with DPRK). Weapons generally weren't(to be fair - DPRK avoided chinese weapons much more than it's generally understood in the west - fear of large China is a basic historical trait for any Korean state). But your statement, as far as I remember, was about the ability to do everything in DPRK, better than?
All those and more were and are available in Russia, with fundamental/industrial/military research continuously stretching back into history. DPRK never had such luxury, and for most part doesn't have it right now - only practical solutions from available components(i.e. doing world-level development from all the same smuggled OTS components everyone else uses. +developing absolutely key capabilities, only there and when they aren't procurable).
This leads to a country, at the same time makes impressive ballistic and space rockets (which is still 1960s-1980s level of tech solutions, not exactly a forefront), and where Japanese tractor in the field is still a valuable asset. Occupation-era Japanese.
Comparing that to what Russia can provide them with is a complete lack of understanding of what and where DPRK is at.