We have an Angular 4 project that I've recently tried to upgrade to Angular 8. I followed the migration guide in Angular website, changed some of the syntaxes, and everything preventing project to be built. I faced the problem of my styles were not loading properly locally and not at all on Azure. 
I found Webpack and tried to configure it, added style-loader, sass-loader, and css-loader. 
Now when I'm running locally, I can see in the network tab in the browser that all styles are loading properly, but it only loads the default index.html file and not bootstrapping the application. 
When I deploy the app on Azure, it loads other components, but none of the styles are loading. I spent 3 weeks on migration, nothing promising yet.
Tools/Plugins version:
Angular CLI: 8.3.5
Node: 10.15.1
OS: win32 x64
Angular: 8.2.7
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... platform-server, router
Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.803.5
@angular-devkit/build-angular     0.803.5
@angular-devkit/build-optimizer   0.803.5
@angular-devkit/build-webpack     0.803.5
@angular-devkit/core              8.3.5
@angular-devkit/schematics        8.3.5
@angular/cdk                      8.2.0
@angular/cli                      8.3.5
@angular/http                     5.2.11
@angular/material                 8.2.0
@ngtools/webpack                  8.3.5
@schematics/angular               8.3.5
@schematics/update                0.803.5
rxjs                              6.5.3
typescript                        3.5.3
webpack                           4.40.2Here is my Webpack config:
const { resolve } = require('path');
const rxPaths = require('rxjs/_esm5/path-mapping');
const CopyWebpackPlugin = require('copy-webpack-plugin');
const ProgressPlugin = require('webpack/lib/ProgressPlugin');
const CircularDependencyPlugin = require('circular-dependency-plugin');
const { AngularCompilerPlugin } = require('@ngtools/webpack');
const { IndexHtmlWebpackPlugin } = require('@angular-devkit/build-angular/src/angular-cli-files/plugins/index-html-webpack-plugin');
module.exports = {
  mode: 'development',
  devtool: 'eval',
  entry: {
    main: './src/main.ts',
    polyfills: './src/polyfills.ts',
    styles: './src/styles.scss'
  },
  output: {
    path: resolve('./dist/'),
    filename: '[name].js',
  },
  resolve: {
    extensions: ['.ts', '.js'],
    alias: rxPaths()
  },
  node: false,
  performance: {
    hints: false,
  },
  module: {
    rules: [
      {
        test: /\.ts$/,
        use: '@ngtools/webpack'
      },
      {
        test: /\.js$/,
        exclude: /(ngfactory|ngstyle).js$/,
        enforce: 'pre',
        use: 'source-map-loader'
      },
      {
        test: /\.html$/,
        use: 'raw-loader'
      },
      {
        test: /\.s[ac]ss$/i,
        use: ['sass-loader'],
        // use: ['to-string-loader, css-loader, sass-loader'],
        exclude: [resolve('./src/styles.scss')]
      },
      {
        test: /\.s[ac]ss$/i,
        // use: ['sass-loader'],
        include: [resolve('./src/styles.scss')]
      },
      {
        test: /\.(eot|svg|cur)$/,
        loader: 'file-loader',
        options: {
          name: `[name].[ext]`,
          limit: 10000
        }
      },
      {
        test: /\.(jpg|png|webp|gif|otf|ttf|woff|woff2|ani)$/,
        loader: 'url-loader',
        options: {
          name: `[name].[ext]`,
          limit: 10000
        }
      },
      // This hides some deprecation warnings that Webpack throws
      {
        test: /[\/\\]@angular[\/\\]core[\/\\].+\.js$/,
        parser: { system: true },
      }
    ]
  },
  plugins: [
    new IndexHtmlWebpackPlugin({
      input: 'index.html',
      output: 'index.html',
      inject: 'body',
      entrypoints: [
        'styles',
        'polyfills',
        'main'
      ]
    }),
    new AngularCompilerPlugin({
      mainPath: resolve('./src/main.ts'),
      sourceMap: true,
      nameLazyFiles: true,
      tsConfigPath: resolve('./src/tsconfig.app.json')
      // ,
      // skipCodeGeneration: true
    }),
    new ProgressPlugin(),
    new CircularDependencyPlugin({
      exclude: /[\\\/]node_modules[\\\/]/
    }),
    new CopyWebpackPlugin([
      {
        from: 'src/assets',
        to: 'assets'
      },
      {
        from: 'src/favicon.ico'
      }
    ])
  ]
};Please note that the reason I've commented use[] in Webpack config was that it was throwing some postcss-loader exception and on an issue on Github found that some conflict will occur with default sass-loader and Webpack and you should remove them.
Here is the build config in angular.json
        "build": {
          "builder": "@angular-builders/custom-webpack:browser",
          "options": {
            "customWebpackConfig": {
              "path": "./webpack.config.js",
              "replaceDuplicatePlugins": true
            },
            "outputPath": "./dist/",
            "index": "src/index.html",
            "main": "src/main.ts",
            "tsConfig": "src/tsconfig.app.json",
            "polyfills": "src/polyfills.ts",
            "assets": [
              "src/assets",
              "src/config",
              "src/favicon.ico"
            ],
            "styles": [
              "./src/styles.scss"
            ],
            "scripts": [
              "node_modules/jquery/dist/jquery.min.js",
              "node_modules/bootstrap/dist/js/bootstrap.min.js",
              "node_modules/metismenu/dist/metisMenu.js",
              "node_modules/vis/dist/vis.min.js",
              "vendor/js/jvectormap/jquery-jvectormap-2.0.2.min.js",
              "vendor/js/jvectormap/jquery-jvectormap-us-mill.js",
              "vendor/js/iCheck/icheck.js",
              "node_modules/toastr/toastr.js"
            ]
          },
          "configurations": {
            "dev": {
              "optimization": true,
              "sourceMap": false,
              "extractCss": true,
              "namedChunks": false,
              "aot": true,
              "extractLicenses": true,
              "vendorChunk": false,
              "buildOptimizer": true,
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.dev.ts"
                }
              ]
            },
            "local": {
              "optimization": true,
              "sourceMap": false,
              "extractCss": true,
              "namedChunks": false,
              "aot": true,
              "extractLicenses": true,
              "vendorChunk": false,
              "buildOptimizer": true
            },
            "production": {
              "optimization": true,
              "sourceMap": false,
              "extractCss": false,
              "namedChunks": false,
              "aot": true,
              "extractLicenses": true,
              "vendorChunk": false,
              "buildOptimizer": true,
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.prod.ts"
                }
              ],
              "styles": [
                "./src/styles.scss"
              ]
            }
          }
        },And here is the serve config in Angular.json.
"serve": {
          "builder": "@angular-builders/custom-webpack:dev-server",
          "options": {
            "browserTarget": "projectName:build",
            "customWebpackConfig": {
              "path": "./webpack.config.js"
            }
          },
          "configurations": {
            "local":{
              "browserTarget": "projectName:build:local"
            }
            ,
            "dev": {
              "browserTarget": "projectName:build:dev"
            },
            "production": {
              "browserTarget": "projectName:build:production"
            }
          }
        },I have imported all styles in styles.scss using @import statements. Just one thing I am not sure about is that I'm using Highcharts and getting some warnings during the build.
WARNING in ./node_modules/angular2-highcharts/dist/index.js
Module Warning (from ./node_modules/source-map-loader/index.js):
(Emitted value instead of an instance of Error) Cannot find source file '../src/index.ts': Error: Can't resolve '../src/index.ts'
Other than these, there is not compile/runtime error in the project.
Thank you for taking the time to read my problem. I appreciate any hint/tip.
Update: This is how the project structure looks like:
|   .editorconfig
|   .gitignore
|   angular.json
|   browserslist
|   karma.conf.js
|   package-lock.json
|   package.json
|   protractor.conf.js
|   README.md
|   tsconfig.json
|   tslint.json
|   webpack.config.js
|          
+---src
|   |   favicon.ico
|   |   index.html
|   |   index.js
|   |   main.ts
|   |   polyfills.ts
|   |   styles.scss
|   |   test.ts
|   |   tsconfig.app.json
|   |   tsconfig.spec.json
|   |   typings.d.ts
|   |   webpack.config.common.js
|   |   
|   +---app       
|   +---assets
|   |   |
|   |   +---images
|   |   \---styles
|   |       |   style.scss
|   |       |   
|   |               
|   +---config
|   |       dev-config.js
|   |       local-config.js
|   |       prod-config.js
|   |       qa-config.js
|   |       
|   +---environments
|   |       environment.dev.ts
|   |       environment.prod.ts
|   |       environment.qa.ts
|   |       environment.ts
  
     
     
    