You can, if you use pledge() and unveil() on Linux. SECCOMP and Landlock use a monotonically decreasing permissions model. It's inherited across exec(). This is a good thing. OpenBSD devs don't need it because they built their own hermetic system. They're more afraid of having their servers compromised remotely than they are of programs they've installed locally. The tradeoff is you can't use pledge() and unveil() to build your own SSH server on Linux, since SSH needs to shed restrictions when launching a shell. But the benefit is you can safely leverage more code written by strangers on the Internet, which is what Linux is all about.