I did some further research on OOM not doing its job and see earlyoom - The Early OOM Daemon:
The oom-killer generally has a bad reputation among Linux users. This may be part of the reason Linux invokes it only when it has absolutely no other choice. It will swap out the desktop environment, drop the whole page cache and empty every buffer before it will ultimately kill a process. At least that’s what I think that it will do. I have yet to be patient enough to wait for it, sitting in front of an unresponsive system.
earlyoom is available as package at least for Tumbleweed.
The is also hakavlad /nohang that has even more relevant documentation on it’s README.md
If you do not want to install additional software for this I found on this page:
For me setting vm.admin_reserve_kbytes=262144 does exactly this thing. OOM killer intervents before system goes completely unresponsive.