I'm currently sorting the AUR clients out, but a few in the official repos:
- audiotube: KDE Client for YouTube Music
- plasmatube: Kirigami YouTube video player based on QtMultimedia and youtube-dl
- streamlink: a plugin-based streaming utility with support for various popular players
- ytfzf: A POSIX script to find and watch youtube videos from the terminal
Edit: i've given up; there's around 300 clients / downloaders in the AUR