The classic way to import web3 in Angular

web3-service.ts

import { environment } from '../environments/environment';
import { bindNodeCallback, Observable } from 'rxjs';

@Injectable({ providedIn: 'root' })
export class Web3Service {

  public web3: Web3;

  constructor() {
    this.web3 = new Web3(environment.web3Provider);
  }

  public getAccounts(): Observable<string[]> {
    return bindNodeCallback(this.web3.eth.getAccounts)();
  }
}