How to use line breaks instead of paragraphs

[Lukasvo]

I'd like to mimic Facebook's behaviour where typing 'enter' doesn't start a new paragraph but introduces a linebreak instead.
However, If they press enter twice, it should start a new paragraph.

How could I implement this?

I've tried writing a plugin that merges a new paragraph with the previous paragraph as soon as it contains any text:

export default function LineBreaksNotParagraphsPlugin() {
  const [editor] = useLexicalComposerContext();

  useEffect(() => {
    // Use linebreaks instead of paragraphs (except when two linebreaks after each other)
    editor.registerNodeTransform(CustomParagraphNode, (paragraph) => {
      const previousSibling = paragraph.getPreviousSibling();

      const mergeWithPreviousSibling = () => {
        previousSibling.append(new LineBreakNode());
        previousSibling.append(...paragraph.getChildren());
        paragraph.remove();
      };

      if (previousSibling?.getType() === 'paragraph' && !paragraph.isEmpty()) {
        mergeWithPreviousSibling();
      }
    });
  });

  return null;
}

This needs to be extended to prevent merging if the previous paragraph is empty (= start a new paragraph when entering two linebreaks), but then I'd need to make sure this paragraph doesn't get merged with the one before subsequently. I tried making a CustomParagraphNode with a flag that indicates if the paragraph can be merged (= it's a linebreak) or not (= it's a paragraph), but without success thus far.

Just keeping the above implementation, which simply replaces paragraphs by <br /><br />, would be acceptable too if it weren't for the fact that you can't set headings, list items etc. anymore, because the whole text is a single paragraph.

Does anyone have recommendations?