@alexzak Hi and welcome to the Forum 
AFAIK earlyoom is the way… Perhaps a peruse of the old thread https://forums.opensuse.org/t/oom-killer-back-active-after-update/145104/
Just a note, make any sysctl changes as conf files down in /etc/sysctl.d/ directory, openSUSE Tumbleweed also moved to /usr/etc so some configs that use to reside in /etc have moved, but can be overridden in /etc/some.d/ directory.