Are there any versions of iOS without jailbreak exploits in them? The security was always theatre.
Recent versions of iOS have specific anti-jailbreak mechanisms (anti-downgrade mechanisms, ephemeral root filesystems) which don't provide general security, so they're sort of cheating. These mechanisms just mean it's harder to use the vulnerabilities for good, without significantly stymieing evil. (And they aren't wholly effective, seeing as 16.6.1 contains all of them, and it's still got a semi-untethered jailbreak.)