I personally don’t use a RSSifier as all the sites I want to subscribe to tend to have a rss.xml or a atom.xml. There is https://rss.app/ which has rss feed generator but I am pretty sure it is not FOSS. Not to mention it uses AI and I don’t like the idea of handing over all the websites I read to a third party company. As for FOSS you would be hard pressed to find one as it is an expensive thing to run. Best thing to do is send a message to the creator of the website you would like a RSS feed. It is not a hard thing to set up and they will probably do it at your request.
Perhaps nobody says they use it out loud although knowing vim users (and being one myself) they tend to be very willing to share how bad a mouse is for productivity while programming and how using vim is the ultimate solution. As for emacs I only ever have seen greybeards use it and it dosen’t to have had much of a revival with the newer generations.