Android 9 pie see if device is encrypted
All devices that run Android 5 and beyond (out of the box) are encrypted. That's probably why you don't see a separate status for device encryption as you see for Ext.SD.
Encryption can be Full-Disk Encryption (FDE)  or File-Based Encryption (FBE). The device is encrypted on first boot using default encryption and once the user sets up lock screen mechanism , that is used for encryption. Relevant extracts


FDE was introduced in Android 4.4 and is supported till Android 9.

Android 7.0 and higher supports file-based encryption (FBE).

For devices running Android 7.0–8.1, file-based encryption can't be used together with adoptable storage.

Devices running Android 9 and higher can use adoptable storage and file-based encryption




For new devices running Android 10 and higher, file-based encryption is required.



Your device being Android 9 with secure start up, it's most likely FBE. You can verify ro.crypto.type on Terminal Emulator and it would show file ( See How can I find out if my device uses FBE or FDE?)