To force the installation of kept-back kernel packages in Ubuntu Linux LTS, you can use the following command:
sudo apt-get install linux-image-generic-lts-<version> linux-headers-generic-lts-<version>
Replace <version> with the desired version number. This command will install the latest version of the specified kernel packages, even if it’s being kept back.
Note: Updating the kernel packages may require a reboot to take effect.