How do I force the dark theme in a “popout” chat URL to Twitch?

If I link to a Twitch chat such as:

Then it shows the default, bright, white theme.

I want the dark theme. That is, some kind of GET variable in the URL to enable this.

Sadly, this does not work:

I didn’t just randomly try that, but based it on this:

Unfortunately, that’s a separate documentation on the “embed” feature, which is clearly different from the “popout” chat links. The “embed” one works in a different manner and for various reasons, I cannot just use that. It has to be the “popout chat” which is simply a URL on their website.

I don’t mean manually setting this in a GUI, logging in to an account or using some kind of client-side script hack!

When searching online, I exclusively find irrelevant search results.