apt-get downgraded kernel

Hi,

So, I did an apt-get update/upgrade, and noticed that the Linode provided kernel was downgraded from 4.14 to the Debian-provided kernel 4.9, obviously because I'm using Debian repositories.

This is just a sandbox VPS, so I'm not overly concerned but is it advisable to keep using Linode's kernel? If so, how do I ensure apt-get uses Linode provided kernels?

Thanks.