I have examined the changelogs for 1809, 1909, 2004 and 20H2. They are very similar, with the only actual difference is the edge updates are not in the 1809 changelog.
The KIR feature was introduced in build 2004, and its interesting to see whilst 1909 has been confirmed by users to have the problem, it didnt get the fix, so my gut feeling is 1809 LTSC is probably affected but probably wont get a fix until next month in a new cumulative patch so am going to not install this month's on my pc.
Also KIR will only get used if the broken patch is "not" security related, meaning my theory about the vGPU thing been the issue is incorrect as that was a security patch.
If I do find out 1809 is not actually affected, I will update in this thread, I appreciate if anyone else already knows this if they would reply, thanks.
Microsoft "could" also decide to be awkward and as a means to get gamers off LTSC might not patch it at all.