There are some breaking changes in Angular 9 for libraries. Per the migration docs for Angular 9:
"ModuleWithProviders type without a generic
Some Angular libraries, such as @angular/router and @ngrx/store, implement APIs that return a type called ModuleWithProviders (typically via a method named forRoot()). This type represents an NgModule along with additional providers. Angular version 9 deprecates use of ModuleWithProviders without an explicitly generic type, where the generic type refers to the type of the NgModule. In a future version of Angular, the generic will no longer be optional.
If you're using the CLI, ng update should migrate your code automatically. If you're not using the CLI, you can add any missing generic types to your application manually."
There are some breaking changes in Angular 9 for libraries. Per the migration docs for Angular 9:
"ModuleWithProviders type without a generic Some Angular libraries, such as @angular/router and @ngrx/store, implement APIs that return a type called ModuleWithProviders (typically via a method named forRoot()). This type represents an NgModule along with additional providers. Angular version 9 deprecates use of ModuleWithProviders without an explicitly generic type, where the generic type refers to the type of the NgModule. In a future version of Angular, the generic will no longer be optional.
If you're using the CLI, ng update should migrate your code automatically. If you're not using the CLI, you can add any missing generic types to your application manually."
https://angular.io/guide/deprecations#modulewithproviders-type-without-a-generic