use mdb pro in submodule, follows the 5min tutorial.

use MDBBootstrapModulesPro

but it shows :

BrowserModule has already been loaded. If you need access to common directives such as NgIf and NgFor from a lazy loaded module, import CommonModule instead.Error: BrowserModule has already been loaded. If you need access to common directives such as NgIf and NgFor from a lazy loaded module, import CommonModule instead.

but MDBBootstrapModulePro does not have this problem

it seems to be the MDBBootstrapModule problem