Just FYI; you can test it by running journalctl -f and then do Alt+SysRq+h.
If it’s working you’ll get sysrq help output into journal:
kernel: sysrq: HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(v) show-blocked-tasks(w) dump-ftrace-buffer(z)
Edit to expand on this:
If you can’t find SysRq key and still want to test if functionality is enabled, you can instead try:
echo h | sudo tee /proc/sysrq-trigger