要解决Angular 9通用服务端渲染GRPC错误，您可以按照以下步骤进行操作：

1. 确保您的项目中已安装了所需的依赖项。在package.json文件中，确保以下依赖项已添加：

"dependencies": {
  "@angular/platform-server": "^9.0.0",
  "grpc": "^1.24.2",
  "grpc-web": "^1.0.6"
}

2. 在Angular应用程序中，创建一个服务来处理与GRPC通信的逻辑。例如，创建一个名为GrpcService的服务：

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';
import { grpc } from 'grpc-web-client';
import { YourGRPCService } from './yourgrpcservice_pb_service';
import { YourRequest, YourResponse } from './yourgrpcservice_pb';

@Injectable()
export class GrpcService {
  private grpcService: YourGRPCService;

  constructor() {
    this.grpcService = new YourGRPCService('http://localhost:8080', null, null);
  }

  public callGRPC(request: YourRequest): Observable {
    return new Observable(observer => {
      grpc.unary(YourGRPCService.YourMethod, {
        request: request,
        host: 'http://localhost:8080',
        onEnd: res => {
          const { status, statusMessage, headers, message, trailers } = res;
          if (status === grpc.Code.OK && message) {
            observer.next(message);
            observer.complete();
          } else {
            observer.error({ status, statusMessage, headers, message, trailers });
          }
        }
      });
    });
  }
}

3. 在您的服务端渲染代码中，确保在导入Angular Universal时对grpc库进行正确的导入。例如，创建一个名为server.ts的文件：

import { enableProdMode } from '@angular/core';
import { createServerRenderer, RenderResult } from 'aspnet-prerendering';
import { AppServerModule } from './src/app/app.server.module';
import { GrpcService } from './src/app/grpc.service';
import { YourRequest } from './src/app/yourgrpcservice_pb';

export default createServerRenderer(params => {
  const grpcService = new GrpcService();
  const request: YourRequest = new YourRequest();
  
  return new Promise((resolve, reject) => {
    grpcService.callGRPC(request).subscribe(
      response => {
        const { AppServerModuleNgFactory, LAZY_MODULE_MAP } = response;

        enableProdMode();

        const moduleRef = AppServerModuleNgFactory.create(global);

        const { AppServerModule, AppModule } = moduleRef.instance;

        const providers = [
          { provide: 'REQUEST', useFactory: () => params, deps: [] },
          { provide: 'RESPONSE', useFactory: () => response, deps: [] },
          { provide: GrpcService, useFactory: () => grpcService, deps: [] },
          ...AppServerModule.providers,
          ...AppModule.providers
        ];

        moduleRef.injector.get(YourGRPCService).preFetchData().then(() => {
          resolve({
            html: response.html,
            globals: {
              appModuleFactory: moduleRef,
              AppServerModule,
              LAZY_MODULE_MAP,
              providers
            }
          });
        });
      },
      error => {
        reject(error);
      }
    );
  });
});

请根据您的实际需求修改上述代码，确保在创建和调用GRPC服务时使用正确的类和方法。

这些步骤应该能够帮助您解决Angular 9通用服务端渲染GRPC错误。请不要忘记将代码中的YourGRPCService和YourRequest替换为您实际使用的GRPC服务和请求对象。