[Bug]: Test browser native inputs such as date input in different languages

Version

1.48.0

Steps to reproduce

Reproduction

1. Clone repo at https://github.com/mello-r/playwright-accept-language-bug
2. pnpm install
3. pnpm test:ui
4. Input date has the English format and not the German as configured in playwright.config.ts

Expected behavior

I expect it will be possible to emulate a different language on the Playwright browser, to have a different format for browser native inputs such as date input.

Here how it looks in locale Firefox:

Actual behavior

I could not find a way to get the Playwright browser to emulate a different language to display the native input date in a different format.

Here how it looks in Playwright:

Additional context

At first, I wrote a comment on this issue in #18609, but mxschmitt told me that this was a different problem and should be a separate issue.

Environment

System:
OS: Linux 5.15 Ubuntu 20.04.6 LTS (Focal Fossa)
CPU: (16) x64 AMD Ryzen 7 5700U with Radeon Graphics
Memory: 15.61 GB / 18.95 GB
Container: Yes
Binaries:
Node: 20.11.1 - ~/.nvm/versions/node/v20.11.1/bin/node
Yarn: 1.22.22 - ~/.nvm/versions/node/v20.11.1/bin/yarn
npm: 10.2.4 - ~/.nvm/versions/node/v20.11.1/bin/npm
pnpm: 9.12.2 - /usr/bin/pnpm
IDEs:
VSCode: 1.94.1 - /mnt/c/Program Files/Microsoft VS Code/bin/code
Languages:
Bash: 5.0.17 - /usr/bin/bash
npmPackages:
@playwright/test: ^1.48.0 => 1.48.0

Start with the linked reproduction repository, install its dependencies with pnpm install, and run pnpm test:ui. Inspect playwright.config.ts and compare the configured language with the native date input shown in the reproduction; done means Playwright can display the input using the configured language format.