Huh, while logged in, my own files downloaded as PowerPoint files but all the other ones I tried downloaded as PDFs.
For just a basic, community curated presentation, PowerPoint files are now editable from within the browser on Google Drive, or to avoid weird compatibility/syncing issues you could just do Google Slides directly. (Similar use case for some general how-to printouts as discussed here: https://forum.inaturalist.org/t/how-to-use-inaturalist-postcards/4911/11)