Just leaving a note here that if you see a signal 31 JVM crash with

[WARN] Install JVM debug symbols to improve profile accuracy
[WARN] open("/proc/kallsyms"): Permission denied

Then some modpack is using spark, the JVM profiler tries to load some stuff for profiling which is restricted in your environment (sandboxing via systemd) and thus this crashes the whole JVM.
Setting backgroundProfiler: false in config/spark/config.json solves that issue.