I'm currently testing the experimental server actions feature in Next.js. Once this feature is enabled Next.js uses React's experimental build. This however results in hydration failed error messages when using custom HTML tags with a dash like `my-tag` in JSX. The server response does not include any output for this tag and its children. Replacing the custom tag with a regular tag like `<div>` works completely fine.

I previously reported this issue at vercel/next.js#51141 where they suspect this to be an issue within React itself.

React version: Experimental

## Steps To Reproduce

1. Install latest next.js: npx create-[next-app](https://linear.app/vercel/issue/NEXT-app)@latest
2. Enable server actions in next.config.js
3. Wrap {children} in root layout with custom HTML tag like `<my-tag>`

Link to code example:
https://github.com/mritzerfeld/next-server-action-with-custom-tag

## The current behavior
Server-generated contents with custom HTML tags do no produce any output for such.

## The expected behavior
Server-generated contents within custom HTML tags to be included in server response, as using Next without server actions or with regular HTML tags.

});
    expect(getVisibleChildren(container)).toEqual([
      <div id="container-A">Loading A...</div>,
      <div id="container-B">Loading B...</div>,
    ]);
    await act(() => {
      resolveText('B');
    });
    expect(getVisibleChildren(container)).toEqual([
      <div id="container-A">Loading A...</div>,
      <div id="container-B">
        This will show B: <div>B</div>
      </div>,
    ]);
    await act(() => {
      resolveText('A');
    });
    
    writable.end();
    expect(getVisibleChildren(container)).toEqual([
      <div id="container-A">
        This will show A: <div>A</div>
      </div>,
      <div id="container-B">
        This will show B: <div>B</div>
      </div>,
    ]);
  });
  it('can resolve async content in esoteric parents', async () => {
    function AsyncOption({text}) {