We are not talking about datacenter servers - we are talking about smartphones. you can run a 4.9 kernel with all security patches applied, just like you can run windows10 with all security patches applied. You can update bluetooth and wifi modems without going to a later kernel version. We call those drivers, not kernels.

The issue you note is only exploitable via a bug if you have an outdated version of the chrome browser. You don't need to update the kernel, in order to update an application.

Seriously, I feel like I'm talking to my wife here, who is not a tech person. Why are you and the other couple of people being purposely dense, and purposely ignoring the content of your own links that doesn't fit your viewpoint?

BTW, after you said smartphones aren't servers, you go on to talk about why an older kernel is bad on servers.

But since you asked, the latest 4.9.3 kernel running on that nexus6 from 2014, that's been compiled appears to be from the end of the year 2019.