https://en.opensuse.org/SDB:SPICE

SPICE was removed from SUSE Linux Enterprise Server 16.X as well as Leap 16.X since openSUSE Leap re-uses binaries from virt stack from SLES.
You can regain the functionality by enabling this repository on your Leap or SLES system.

The idea is to simply rebuild exactly same sources from SLES under openSUSE with SPICE enabled.