So, as for South Korea :
Obviously best is to dig primary sources like budget plans, audit reports and research publications using a translator but I could understand that doing so is very hard and time consuming as non-Korean speakers (and frankly, even for native speakers, too).
There's also another layer of problem that access to academic sources could be limited unless you are in a university or you have institutional access (or you find them pirated). Even if you do, often times Korean research papers are only published in Korean publication service that doesn't support western Institutions so it becomes even harder.
So instead for trustable secondary sources, I'd like to first recommend Sheldon's Patreon (
https://www.patreon.com/cw/jhst3103 ) for the most up-to-date, in-depth and accurate articles. He is a blogger that visits various important conferences and symphosia as well as trade fairs as freelance journalist and do his own research as well. Unfortunatley he only recently started publishing in English through Patreon, and most of his older (yet still very helpful) posts are still yet to be translated in English. I'm not sure if he ever will, but since one could use some AI help these days, hopefully he will. Also, his contents are paywalled so unless you are really deeply interested in matters in Korea, you might as well want to wait for the information to get more accessible.
Another recommendable source is HyunSH's blog (
https://blog.naver.com/kevin1406). Similar to Sheldon, but his contents are free. Though you have to remember free contents are free for a reason. It isn't as in-depth, or broad as Sheldon's but I'd say good enough. Also it's a blog, so keep in mind that errors are always possible.
As for news outlets, I'd recommend Defensetoday.kr. Unfortunatle there aren't many defence related media outlets in Korea and this one is one of the better ones out there.
Discussion concerning military is most active on "military" board on Dcinside.com (or as its called in Dcinside, "Gallery"), which is very similar to Reddit in terms of the system and is the biggest 'news aggregate and forum social media' platform in Korea. As you would expect from one such social media platform, that is 'similar to reddit and is popular', content you could find here are either overwhelmingly low-effort rubbish, or vastly misinformed. There are some good contributions by few recurring contributors, but they are rather rare. As a result, not recommended unless you have plenty of time to waste to sort out the bad crops from the good ones.
There are also other defence and aerospace related forums that used to be popular in the past, but all of them have faced significant decline over the years. Forums like Bemil.chosun.com and Milidom.net were almost equally as popular as military board of Dcinside.com, but nowadays you'll find that there is almsot no activity in these forums. Their use are more suited as sources for legacy programmes, so they are in a way similar to Keypublishing, although they aren't completely dead unlike KeyPub.
Another reason I think it is hard to find information regarding stuff going on in South Korea is because the English Wikipedia page is pretty rubbish when it comes to topic concerning Korean aerospace and defence industry and the military and Korean Wikipedia is even worse across the board. Part of the reason is that the primary wiki in South Korea is Namu.wiki. Problem with Namu.wiki though, is that the rules are much more lax about citing sources, and as a result the quality of each articles varies a lot, and by that I mean A LOT. Might be useful if you want to have some overview and find some Korean keywords that you could use for further research.
There might be a few more that I could recommend, but for now these are it.
