I can share to Termux from the YouTube app on my Pixel and download an entire playlist to my music folder - Ffmpeg handles any audio.
It's quicker than any of the YouTube downloader apps I've tried!
How it works: in ~/bin there's a termux-url-opener script that handles what you share:
"#!/bin/bash
case "$1" in
*youtu*)
echo "$1 is a YouTube URL,
downloading"
sh ~/shortcuts/dl_yt.sh $1
..."
(dl_yt just calls youtube-dl -x)
I love it and am still finding new uses for Termux. I've got neovim and all my dotfiles loaded, so in a pinch I can ssh into my phone to do some work.