

“The cloud” is somebody else’s computer. Somebody else leases you the space and compute, somebody else can turn the physical machine off or terminate your access to their service. Self-hosting is about removing as many somebody-elses as possible (you’re still on the hook for stuff like power and an ISP, though a lot of self-hosted stuff is also designed to function purely offline so it’s just power for that stuff).
yt-dlp, but most of the time you’ll use some form of front end. All the “youtube downloaders”, even the shady websites, are using yt-dlp. For selfhosted purposes, I like MeTube for individual downloads and Tubesync for keeping up with channels.