Going by CVEs, Haiku is more secure than OpenBSD. Linux has had strong kernel-level crypto enabled by default on major distributions for years, see AF_ALG or LUKS.

On the wiki page you provided, the only thing that really stands out at the kernel level is KARL, which has a dubious utility: https://isopenbsdsecu.re/mitigations/karl/ It is not even up to date: strlcpy(3) and strlcat(3) were implemented in glibc 3 years ago.