AOSP docs use the terms traditional and adoptable storage… see https://source.android.com/docs/core/storage/traditional
Only adoptable can be encrypted as of writing, and as my prior posters noted, if the sdcard is somehow corrupted when adopted, you’ll have to go full reset.
So the current state is a bit sad, you’ll need to use 3rd party apps to create encrypted storage on the “traditional” sdcard. “EDS Lite” App comes to mind. Then there are modules for LUKS that you can employ if you have root - but not straightforward: