I have the S8 Active and recently upgraded to Pie. Since the update, the phone has a new password screen after reboots that says it has been encrypted. I cannot find anywhere to turn this off.
The SD card can be encrypted and decrypted. Please go to Settings>Biometrics and Security and decrypt the SD Card. You can also change the lock screen settings to Swipe.
Go to 'settings', 'biometrics and security', and set 'secure startup' to 'do not require' and press 'apply'.
Problem should be solved.
Not sure why this moderator didn't immediately say this.