They're talking about secure boot up.. The phone won't start at all unless you have a PIN.
I looked for it too! I don't think it's here
This is not completely true. Your data is still encrypted even while your device is on the lock screen. But the stronger your pin or password is the greater the encryption. So it is not "wide open" as you think it is.Can't find it either and it doesn't seem to work for me like it used to on S9+. I have PIN and fingerprint unlock setup. On restarting the phone it boots it all the way into Android UI asking for 1st time unlock, which is similar to every other older phone I've had. What it doesn't do for me is showing PIN unlock screen before continuing booting into Android UI.
Tried a few things like changing from PIN to password for instance, which made no difference.
That's a series issue IMHO. Secure startup prompts for PIN before storage is decrypted so technically w/o that your data is wide open if someone gets a hold of your phone.
Has anybody managed to get it working?
Settings > biometrics & security > other security settings > strong protections
I have this enabled on mine especially if you want more security. But just to be clear this is not the secure boot the OP was asking about.Settings > biometrics & security > other security settings > strong protections
Maybe because they added this feature they felt that Secure Boot was no longer needed.I've played with that too, that's not it.