Comment # 5 on bug 1186320 from Takashi Iwai

(In reply to Jon Harrison from comment #3)
> To verify I am doing this correctly:
> I added your pkg with zypper ar
> I refreshed zypper
> I run zypper dup -r
> 
> This removed a bunch of files and added the kernel-macros from your pkg.

Erm, this was way too much and dangerous.
It's fairly trivial to install a kernel package.  A safer way would be just to
download kernel-default-5.*.rpm from the download URL, then install the file
like
  zypper in --oldpackage kernel-default-*.rpm

(The --oldpackage option is often required because the unofficial build has
usually lower release number.)

That's all.  Once after you test a new kernel and no longer need it, check the
currently installed kernels via
  rpm -q kernel-default
and uninstall the one via
  zypper rm kernel-default-xxx
where filling -xxx with the exact version-release numbers to be uninstalled.