By default, Ubuntu LTS release stay on the same Linux kernel they were released with. The hardware enablement stack (HWE) provides newer kernel and xorg support for existing Ubuntu LTS release. Things have been changed recently. If you downloaded Ubuntu 18.04.2 or newer desktop version, HWE is enabled for you and you’ll get the new kernel along with the regular updates by default.
For server versions and people who downloaded 18.04 and 18.04.1, you’ll have to install the HWE kernel. Once you do that, you’ll get the newer kernel releases provided by Ubuntu to the LTS version.
See how to do this at https://itsfoss.com/ubuntu-hwe-kernel/.
Of course though if you have Manjaro Linux its as easy as running the kernel application (pictured), clicking to install and rebooting.