I'm surprised there haven't been posts about it (or at least I haven't seen them on all the usual suspect communities). My guess is that people are hesitant to call it out in case the story turns out to be true, but I have no such qualms.
How it started
It started when Kyiv Independent quoted a "Western source" that the DPRK has sent 10.000 troops to Russia,. The Western media then ran with the story and said Ukrainian intelligence believes DPRK soldiers are sent to Russia. Once Zelenskyy started talking about it that was good enough for Western media to accept it as fact. I can't find the article now, but I distinctly remember a headline saying "Zelenskyy confirms North Korean soldiers fighting for Russia", they must have changed the headline because of how it sounds. I need to remember to take more screenshots.
At the same time as this story was "breaking", the Western media ran a parallel story about how the DPRK soldiers have already fled their positions. Of course, no videos or pictures of these "deserting soldiers" were ever posted or shared. The Western audience believes these things because they want to believe them to be true.
Racist undertones
Ukraine+Western media are saying that Russia is going to use the DPRK troops to form a Buryat battalion. Buryat people are a distinct ethnicities within the Russian Federation. Ukrainian intelligence services have no doubt chosen the name "Buryat battalion" because in low quality videos and photos Western audiences are not expected to know the difference between a Buryat soldier and a Korean soldier. They are also claiming the Koreans are receiving Russian passports, documents, etc. so if they ever come across the bodies of dead Buryat soldiers they can just claim those are actually DPRK soldiers.
How it's going
The latest "evidence" posted of these supposed DPRK soldiers "fighting for" Russia is two videos without a date or location, but purportedly from Russia's far east. In both videos you can hear Korean being spoken. In one video they are outside training, and in the other they are receiving Russian uniforms.
The Western media can't even get their story straight though. First they reported that South Korea's intelligence has said 12000 DPRK soldiers are fighting for Russia in Ukraine but then they revised their story to say 1500 DPRK troops are fighting for Russia. If you look at the CNN url, you will see that it still says "12000 troops", although the title and the body of the article have changed.
Why are they saying this?
It is obvious that Zelenskyy & Co. are trying to present this as an escalation and evidence that this is becoming a "world war". The fact that Ukraine has been supported by countries from around the world is irrelevant. They claim 1500 DPRK citizens getting Russian uniforms is a big problem, yet when some 20.000+ mercenaries from the West received Ukrainian uniforms that was actually wholesome big chungus move.
Regardless of the reality, most people in the West now think that DPRK soldiers are actually fighting Ukraine on the ground, despite the fact that "NATO has not confirmed that thousands of North Korean troops are preparing to join the war, Secretary-General Mark Rutte said on Thursday."
But what if the Western media turns out to be right, and there are DPRK soldiers fighting in Ukraine?
I'm happy to say that this story is bullshit because what are 1500 soldiers going to do for Russia? Russia supposedly has some 400k soldiers in Ukraine right now. According to Ukraine+Western media, Russia suffers 1000-1200 casualties a day, so DPRK just sent them a day's worth of fighting force.
But even if that were true (and it isn't), it's not a big deal. Where was the outrage six months ago when Macron said he is considering sending French troops to Ukraine? People don't seem to understand that nobody is stopping individual countries like Poland, Estonia, Latvia, etc. to send troops to Ukraine. It won't trigger Article 5 and it won't drag NATO into war. But no country wants to do it, and no country will do it in response to 1500 supposed DPRK troops being sent there.
If DPRK troops are indeed in Russia and Ukraine, then they are there probably for training, education or to oversee the transfer and use of the artillery ammunition they had sent to Russia earlier. NATO has thousands of its own personnel working in Ukraine, in addition to all the removed and spies.
The media loves this story because now it's Ukraine "alone" versus Russia, Iran, China and North Korea. It feeds into their underdog story, which only works if they completely ignore all the assistance Ukraine received from the West from the start of this war.
Probably, you are right. But it is sadly so vague regarding evidence