It's very easy to bork your system with UKUU:
Source: https://wiki.ubuntu.com/Kernel/MainlineBuildsBy default, Ubuntu systems run with the Ubuntu kernels provided by the Ubuntu repositories. However it is handy to be able to test with unmodified upstream kernels to help locate problems in the Ubuntu kernel patches, or to confirm that upstream has fixed a specific issue. To this end we now offer select upstream kernel builds. These kernels are made from unmodified kernel source but using the Ubuntu kernel configuration files. These are then packaged as Ubuntu .deb files for simple installation.
These kernels are not supported and are not appropriate for production use.
Source: http://www.omgubuntu.co.uk/2017/02/ukuu ... nel-ubuntuYou should not assume these kernels will be reliable enough for everyday use. You install them at your own risk. Be aware that as these are pure upstream releases they do not include any Ubuntu-specific drivers or patches, nor any proprietary modules or restricted binary drivers.
Even if you know how to boot from an older kernel, in case of kernel failure: you risk losing important work because of an unstable and unreliable kernel.