I just took a look at the videos I’ve downloaded using JDownloader2. I’ve downloaded around fifty over the past couple of years.
Quite a few of them are long out-of-print musical recordings. By default, JDownloader2 downloads from YouTube an MP4 video file, an M4A audio file, and other files, including transcripts or captions, if available, so the M4A files are easily imported into Apple Music or iTunes.
A high school classmate uploaded a collection of decades-old school videos that were too precious not to download. Old band performances, football games, graduation clips, and so on.
I’ve also downoaded some videos to be edited down and used later as clips in educational materials under “fair use” terms.
Just between us, I admit to downloading an obscure audience-filmed rock concert clip or two.
Edited to ad: No ads, either!