Install the followig at least: VLC in Android, `jq`, Termux API, `youtube-dl`, `streamlink`, `gallery-dl` and `aria2c`

termux-url-opener

#!/data/data/com.termux/files/usr/bin/bash
if [ -z "${1:-}" ]; then
	exit 1
fi

url_is_supported() {
	REPLY=""
	declare -A arr

	case "$1" in
		*youtube.com/watch*|https://youtu.be/*)
			if command -v youtube-dl >/dev/null 2>&1; then
				arr[ydl]=0
			fi
		;;

		*)
			# threading in Python is slower than this...
			if command -v youtube-dl >/dev/null 2>&1; then
				printf 'import os\nfrom youtube_dl import extractor\nfor e in extractor.gen_extractors():\n if e.suitable("%s") and e.IE_NAME != "generic":\n  os._exit(0)\nos._exit(1)' "$1" | python &
				arr[ydl]=$!
			fi
			if [ -d /data/data/org.videolan.vlc ]; then
				if command -v streamlink >/dev/null 2>&1; then
					printf 'import os\nfrom streamlink import Streamlink\ntry:\n Streamlink().resolve_url_no_redirect("%s")\nexcept:\n os._exit(1)\nos._exit(0)' "$1" | python &
					arr[slk]=$!
				fi
			fi
			if command -v gallery-dl >/dev/null 2>&1; then
				printf 'import os\nfrom gallery_dl import extractor\nif extractor.find("%s") is not None:\n os._exit(0)\nos._exit(1)' "$1" | python &
				arr[gdl]=$!
			fi

			for k in "${!arr[@]}"; do
				wait "${arr[$k]}"
				arr[$k]=$?
			done
		;;
	esac

	if [ ${arr[ydl]+bleh} ] && [ "${arr[ydl]}" -eq 0 ]; then
		REPLY="video - download,audio - download,vlc - stream (youtube-dl)"
	fi
	if [ ${arr[slk]+bleh} ] && [ "${arr[slk]}" -eq 0 ]; then
		REPLY="${REPLY:+$REPLY,}vlc - stream (streamlink)"
	fi
	case "$1" in
		*soundcloud.com/*)
			if command -v scdl >/dev/null 2>&1; then
				REPLY="${REPLY:+$REPLY,}scdl - download"
			fi
		;;
	esac
	if [ ${arr[gdl]+bleh} ] && [ "${arr[gdl]}" -eq 0 ]; then
		REPLY="${REPLY:+$REPLY,}image - download gallery"
	fi
	if command -v aria2c >/dev/null 2>&1; then
		REPLY="${REPLY:+$REPLY,}aria2c - download"
	fi
	if [ -z "$REPLY" ]; then
		exit 1
	fi
}

youtube_dl_with_common() { youtube-dl --ignore-config --no-call-home --add-metadata --no-mtime --restrict-filenames --cookies "$cookies" -o "$ytdir"'/%(extractor_key)s/%(title).20s.%(ext)s' "$@"; }

downloads="$HOME/storage/downloads"
ytdir="$downloads/yt-dl"
cookies="$downloads/cookies.txt"
# shellcheck disable=SC2064
trap "rm -f $cookies" INT QUIT TERM EXIT

url_is_supported "$1"
set -euo pipefail
if [ "${#1}" -ge 44 ]; then
	len=32
	ellipsized_url="${1:0:len-3}...${1: -$len}"
fi
program="youtube-dl"
case "$(termux-dialog spinner -v "$REPLY" -t "${ellipsized_url:-$1}" | jq -re '.text | select (.!=null)')" in
	video*)
		youtube_dl_with_common -f 'bestvideo[height<=?720][fps<=?30][vcodec!=?vp9][protocol!=http_dash_segments][ext=mp4]+bestaudio[ext=m4a]/best' --write-info-json "$1"
		;;
	audio*)
		youtube_dl_with_common --extract-audio --audio-format mp3 --audio-quality 0 --metadata-from-title '%(artist)s - %(title)s' --embed-thumbnail "$1"
		;;
	'vlc - stream (youtube-dl)')
		decodedurl="$(youtube-dl -f best --ignore-config --no-call-home --cookies "$cookies" -g "$1")"
		if ! am start -R 2 -S -n org.videolan.vlc/org.videolan.vlc.gui.video.VideoPlayerActivity -a android.intent.action.VIEW -d "$decodedurl"; then
			am start -a android.intent.action.VIEW -t video/mpeg -d "$decodedurl"
		fi
		exit 0
		;;
	'vlc - stream (streamlink)')
		streamlink --config=/dev/null --player-http --player=bash -a '-c '\''am start -W -S -n org.videolan.vlc/org.videolan.vlc.gui.video.VideoPlayerActivity -a android.intent.action.VIEW -d '\''{filename}'\'' ; read -n 1'\''' "$1" best
		exit $?
		;;
	scdl*)
		program="scdl"
		"$program" --path "$ytdir" -l "$1"
		;;
	image*)
		program="gallery-dl"
		"$program" --ignore-config --no-mtime --write-metadata --cookies "$cookies" -d "$ytdir" "$1"
		;;
	aria2c*)
		program="aria2c"
		if command -v youtube-dl >/dev/null 2>&1; then
			ua="$(youtube-dl --ignore-config --no-call-home --dump-user-agent)"
		else
			ua='Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3688.1 Safari/537.36'
		fi
		echo "$1"
		"$program" --no-conf --always-resume=false --max-connection-per-server=4 --file-allocation=none --auto-save-interval=0 --enable-http-pipelining=true --user-agent="$ua" --load-cookies="$cookies" --dir="$downloads" "$1"
		;;
	*)
		exit 0
esac

set +e
if [ "$program" != "aria2c" ]; then
	termux-media-scan -r "$ytdir"
fi
termux-notification --title "$program" --content "Completed: $1" --id 69 --priority low

This is a really cool idea! I'm doing a similar thing on my desktops/notebooks and now I'm considering using Android more because of this your idea!