As this wiki Ubuntu page says:
By definition the mainline kernel builds are made from virgin
unaltered mainline kernel sources and therefore do not, and should
not, include any Ubuntu patches or drivers. There are also no binary
drivers for these kernels.
I wonder what is the difference between an Ubuntu mainline kernel and a linux kernel?
Best Answer
Here is a brief answer.
Mainline kernels are just vanilla kernels from kernel.org packed as deb.
Ubuntu kernels are specially maintained by Canonical Kernel Team.
The team backports bug fixes and support of some new hardware from the latest mainline kernels, and also does other improvements.
Canonical and the community supports only the Ubuntu kernels. You can install the mainline ones at your own risk.