Looking at the Feature Request thread that they've been updating, it doesn't look like there are plans for either currently. Probably because you can access them through Amazon. If you have Prime and the Amazon downlader module in Streamfab you can download any of the premium channels that are available for sign up through Prime, so in that regard they already are supported. I know one of those (Starz I think) puts an obnoxious watermark on all of their content so not really worth it in my opinion.
Paramount Plus has its own module in StreamFab but I actually switched to using the Amazon downloader for it because it seems to deliver better quality even though they're both technically 1080p so that could be potentially the same story with Showtime.
