[Milhouse]

With the release last week of Ubuntu 18.04LTS, isn't kernel 4.15.y considered current LTS? Just curious, maybe I'm not understanding the difference.

LTS relates to the whole of the Ubuntu 18.04 OS and has nothing to do with the kernel they have used (which is 4.15.y and as mentioned by @fritsch this kernel is already EOL but presumably what Canonical were testing with prior to release). In future Canonical will no doubt update Ubuntu 18.04 to use 4.16.y and later kernels over the next 2 years or however long they will support 18.04.

LibreELEC releases are not themselves LTS, but the argument is to use an LTS kernel that will likely continue to receive updates throughout the lifetime of the LibreELEC release, rather than use a kernel which will become EOL after as little as 3 months potentially forcing LibreELEC to switch mid-release from 4.15.y to 4.16.y or whatever kernel is the latest kernel during the approximate 1-year lifespan of any LibreELEC release.

Releasing only LTS kernels with LibreELEC has major downsides IMHO, however, which will only become more apparent over time.