LTSC: What is it, and when should it be used?

To be honest, I really do not see how you have such a big issue keeping up to date on Windows 10. First off, LTSC is a bad choice for close to every user in any case, to many potential pitfalls and limitations. It's an embedded/IoT solution.

Managing computers without management tools is not easy, but if your are serious you should also be serious managing your computers, making sure they are up to date and compliant. With an increasing degree of travel and out of office usage, as well as interaction with external systems and users, firewalls are not the most important point of security any more, the endpoint is. Not having absolute control of the endpoint can turn out more expensive than you might think.

I'm using a combination of SCCM and Intune managing endpoints, and as a single admin I manage thousands of devices, Windows, iOS and Android, in a more diverse, both geographically and methodically, environment than most other businesses. 

As for the 1806 issues, well, I did not experience any. Nor did I have any issues with any other release either. My impression is, most people did not have any issues, but a small percentage of close to a billion devices is still many systems and users. When the new release is out, I wait a few weeks before I update a small set of test computers in my office. I do some testing trying to provoke some errors, while also looking for people having issues online, trying to identify HW and SW setups common for our environment. I then deploy the update to a set of chosen early adopters/power users, yeah, they know they are guinea pigs, and let them run the new the update for a while. I then deploy for the entire organisation. All data is stored off device, and a full device rollback takes about one hour, should something go bad. So far I've had issues with one upgrade on one computer, out of several thousands. And, after redeploying the OS, every update since were ok.

In a perfect world we would have more people testing every computer type with every software before deploying the upgrades, but needless to say, this is not possible with just one person managing clients. At some point, something might go wrong, we all know this. But we have disaster recovery plans, and most users can do a OSD from their own desk getting the system operational within the hour.

We find that keeping the endpoints secure and compliant is more important in the long run.

AndresPae Nobody said do not use LTSC, and your example of static, automated systems, conducting the same tasks over and over, with little use of new features, doing nothing but these specific tasks, well this could be one of the use cases where LTSC is the best choice. Just think it through first.