Blazor has its own routing system and you can use it in your applications. ABP doesn't add any new feature to it, except one small improvement for the modular development.
Blazor Router component requires to define AdditionalAssemblies when you have components in assemblies/projects other than the main application's entrance assembly. So, if you want to create razor class libraries as ABP modules, you typically want to add the module's assembly to the AdditionalAssemblies. In this case, you need to add your module's assembly to the AbpRouterOptions.
Example
Configure<AbpRouterOptions>(options =>
{
options.AdditionalAssemblies.Add(typeof(MyBlazorModule).Assembly);
});Write this code in the ConfigureServices method of your module.
AbpRouterOptions has another property, AppAssembly, which should be the entrance assembly of the application and typically set in the final application's module. If you've created your solution with the application startup template, it is already configured for you.
- Blazor Routing (Microsoft Documentation)