youtube-dl was replaced with
yt-dlc which is a community fork of
youtube-dl. This was required due to the DMCA take down nonsense that made the original repo disappear.
The command is
youtube-dlc (it behaves the exact same way) personally I have an alias set for best quality settings:
alias ytdownload="youtube-dlc -f 'bestvideo[ext=mp4]+bestaudio[ext=m4a]/bestvideo+bestaudio' --merge-output-format mp4"
So with that set I only have to type: