Exporting video with a transparent background

I’ve seen several discussions on exporting transparent videos here, but I still don’t understand if it can be done, and if so how. I set the background of the document to be transparent, and add the CSS to have a transparent body, but it seems that the scene has a white background so the exports always have a white background. Ultimately I’m interested in exporting a video, which I don’t think is directly supported yet, although this should in theory be possible at least through PNG export. Is there a way to do it now? If so how? Thanks.

this is the current state …