Repository: create-react-app
Issue: All URLs only serve index HTML using TypeScript template
Labels: needs triage,issue: bug report

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### Describe the bug

Immediately after running a fresh `npx create-react-app . --template typescript` I wanted to preview the app and start coding, so I run `npm start`. However, the localhost tab is empty, and when I inspect it the dev server just gives raw HTML for all endpoints, so the 'JavaScript code' my browser loaded was HTML! This is a fresh project from the TypeScript template.

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I solely use NPM for my project, and I emptied everything but README.md before setting up the project.

### Which terms did you search for in User Guide?

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I have scanned the issue, but 

### Environment

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I decided to ditch TypeScript and use the plain version (that works). Since I lost the originals, here's one for the plain template:
```
Environment Info:

  current version of create-react-app: 5.0.1
  running from /home/codespace/.npm/_npx/c67e74de0542c87c/node_modules/create-react-app

  System:
    OS: Linux 6.2 Ubuntu 20.04.6 LTS (Focal Fossa)
    CPU: (2) x64 AMD EPYC 7763 64-Core Processor
  Binaries:
    Node: 20.10.0 - ~/nvm/current/bin/node
    Yarn: 1.22.19 - /usr/bin/yarn
    npm: 10.2.3 - ~/nvm/current/bin/npm
  Browsers:
    Chrome: Not Found
  npmPackages:
    react: ^18.2.0 => 18.2.0 
    react-dom: ^18.2.0 => 18.2.0 
    react-scripts: 5.0.1 => 5.0.1 
  npmGlobalPackages:
    create-react-app: Not Found
```

I am using Codespaces to develop my application, and I have made both projects on the same folder, repo, and instance with no shutdowns.

### Steps to reproduce

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1. Make an empty Github repo
2. Make and open a Codespace for that repo
3. Create the project with `npx create-react-app . --template typescript` on the repo folder
4. Run `npm start`
5. A browser window should auto-open and ports should be forwarded (I use the desktop VS Code)
6. Open DevTools, and a JavaScript error shows

### Expected behavior

It should start normally like the javaScript version.

### Actual behavior

The server returns the index HTML on all routes, thus the browser fails to parse the incorrect JavaScript and React doesn't load.

### Reproducible demo

No demo is needed. This is a dev server issue, and I did not touch anything so create-react-app@5.0.1 should be enough to repro. I suspect the template plays a role since the plain one works.