Does device authorization grant flow support self-hosted login widget?

Whist the Okta device authorization grant flow appears to work with an Okta-hosted signin widget, it doesn’t seem to work with a self-hosted widget. By this, I’m specifically referring to the
https://${yourOktaDomain}/activate endpoint.

Is there a way to get this endpoint to redirect to an externally hosted widget, or alternatively a way of initiating the UI aspect of the device authorization flow via API?

I also note that the current documentation is specifically for the “classic” identity engine. How different is this process under OIE?