How to set local_listener to null upon creating database
I tested specifying -initparams local_listener='' but the local_listener has been set anyways by specifying the empty string.

dbca -silent \
 -createDatabase \
 -templateName General_Purpose.dbc \
 -gdbName testdb \
 -sid testdb \
 -createAsContainerDatabase false \
 -SysPassword oracle \
 -SystemPassword oracle\
 -emConfiguration NONE \
 -datafileDestination /oradata \
 -storageType FS \
 -characterSet AL32UTF8 \
 -memoryPercentage 10 \
 -initparams local_listener=''


You might want to create a custom template referencing a .sql script with the command alter session set local_listener.

I'd only make that effort if in need to use it multiple times, though. If it is a one time thing, maybe you're better off setting local_listener manually.