I am not asking how to do it, but if it is recommended and what is the concern about it.
I have recently seen that the 4.16 Kernel release was at its end of life and that users were urged to upgrade to 4.17. So I checked my version, and I am currently using the Linux 4.15.0-23-generic Kernel on my up-to-date Ubuntu 18.04...
Is this normal? Why is that this way? Is Ubuntu using an out of date kernel? Should I upgrade manually?
I clarify that there are similar questions, but those I found on this forum did not answer my question at all, so I ask again. I do not consider this a duplicate.
Thank you in advance.
Not all kernels are LTS.
Like Ubuntu releases (where even.year april release = LTS), their is no formula that applies to Linux Kernels. You need to watch mailing lists of the kernel devs for their announcements on which are LTS or their supported ranges.
Ubuntu is not built on short-life kernels. Further Ubuntu LTS releases have their kernels supported for the life of their release.
For example,
the linux kernel 4.4 as used in Ubuntu 16.04 LTS reaches its [expected-]EOL in Feb.2022, which is further into the future than Ubuntu 16.04's EOL of April.2021
source: https://www.kernel.org/category/releases.html
Ubuntu LTS releases generally use kernels declared [by upstream LKML] to be LTS; and any kernel used by Ubuntu will at least be supported as long as its release is (by upstream or Canonical). Kernels don't include the the LTS label as visible as Ubuntu itself does.