On the one hand, security guidelines are fairly OS independent. Likewise, it helps whether it's self hosted or not.
On the other hand, I guessed most people would post Linux stuff, so I added FreeBSD content for those who want an alternative or a heterogeneous infrastructure.
- Basics
https://www.freebsd.org/cgi/man.cgi?security
- Baseline Hardening
https://github.com/uxtely/ops-utils/tree/main/location-serve...
- Networking (Firewall, Jails/Containers)
https://blog.uidrafter.com/freebsd-jails-network-setup