Okay first we're gonna have to make sure you can boot to the generic kernel .. because you need to be booted into this kernel to remove the lowlatency kernel.
So...
Shut down your PC
Power ON your PC, and as soon as the BIOS POST screen (manufacturer logo) disappears, hit and hold the "
Shift" key .. you should be presented with the GRUB menu.
On the GRUB menu use the down arrow key to select "
Advanced" .. and hit
Enter.
Use the arrow key to select
Peppermint GNU/Linux, with Linux 4.4.0-87-generic .. and hit
Enter to boot that kernel.
Once you're at the desktop, run:
and post the output back here so I can see you got it right.