Script to auto-update Discord on Linux when you have a manual install with a tarball. Change $BIN_DIR and $DOWNLOAD_DIR to fit your locations.

linux_discord_launcher.sh

#!/bin/bash

# Setup:
# Change BIN_DIR to one folder *above* where your Discord is installed
# and set DOWNLOAD_DIR to whatever directory you want the temporary
# download to go to.
#
# Then simply launch this script instead of the Discord executable.

DISCORD_URL="https://discord.com/api/download?platform=linux&format=tar.gz"

# User custom variables
BIN_DIR="/level/above/discord"
DOWNLOAD_DIR="/your/downloads/directory"

DISCORD_DIR="$BIN_DIR/Discord"
INFO_FILE="$DISCORD_DIR/resources/build_info.json"

CURL_WRITE_OTP="%{redirect_url}"

CURRENT_VER=$( \
    cat $INFO_FILE | \
    sed -z "s/\n/ /g" | \
    python -c \
        "import json; d=json.loads(input()); print(d['version'])"
)

CURRENT_URL=$(\
    curl -Is -o /dev/null \
    -w $CURL_WRITE_OTP \
    $DISCORD_URL
)

LATEST_VER=$( echo $CURRENT_URL | cut -d "/" -f 6 )
LATEST_FILENAME=$( echo $CURRENT_URL | cut -d "/" -f 7 )

if [ $CURRENT_VER != $LATEST_VER ]; then
    wget -O $DOWNLOAD_DIR/$LATEST_FILENAME "$DISCORD_URL"
    tar -xvf $DOWNLOAD_DIR/$LATEST_FILENAME -C $BIN_DIR
    rm $DOWNLOAD_DIR/$LATEST_FILENAME
fi

$DISCORD_DIR/Discord