Kali Linux
7.5#1 in operating systemsFree planFree planAndroidLinuxmacOSSelf-hosted
VisitKali Linux is aimed at experienced penetration testers and security specialists who are familiar with Linux. Its supported environments include computers, virtualized systems, cloud, containers, ARM devices, and Android through Kali NetHunter.
OpenIndiana suits people running 64-bit x86 workstations, servers, or PCs who want a free Unix-like system. It also fits administrators needing IPS package management, boot environment tools, and optional SFE or pkgsrc repositories.