Thanks to me never deleting anything, ever, I know exactly what I was trying to reference cause I was able to find the installers on one of my archive drives.
Here's youtube-dlg.
https://github.com/MrS0m30n3/youtube-dl-gui
Here's yt-dlg.
One works. The other doesn't. Both, IIRC, install themselves as yt-dlg in Windows. Oh, and for more fun, check their contributors out:
Spoiler alert, they renamed youtube-dl-gui to yt-dlg sometime in 2019 and just didn't bother to update the old repo or tell anyone, and eventually youtube-dl-gui stopped working because I'm pretty sure youtube-dl-gui used youtube-dl (aka ytdl), which was similarly forked into yt-dlp and stopped working.
Because it's all the same fucking things as that XKCD comic about Engineers doing manuals: "If you don't understand, that's just because you're stupid."