Comment # 1 on bug 1140259 from Raymund Will

Berthold, would you mind to install `zipl` from SLE15SP1's `s390-tools`,
best together with a kernel from there?

Using `grub2-install --force` should give you a `/boot/zipl/config` with both
kernels, and an IPL with `loadparm=prompt` should make them "selectable"...