Update deb package with libappindicator3-1 dependency to use libayatana-appindicator3-1 instead. For Debian 11.

fix-libappindicator.sh

#!/bin/bash

# Copying: Public domain.

set -e

sourceName=$1

if [[ $sourceName == "" ]]; then
	echo "Usage: fix-libappindicator.sh <.deb>"
	exit 1
fi

pwd=$(pwd)
source="${pwd}/${sourceName}"
targetName=$(echo ${sourceName} | sed s/\.deb/\.new\.deb/g)
target="${pwd}/${targetName}"

workdir=/tmp/fix-`date +%s`
controlWorkdir=${workdir}-control

# Extract the debian package

mkdir $workdir
cd $workdir

ar x $source

# Check whether we have a .tar.gz or tar.xz

controlFile=$(find -name control.tar.*)
controlType=${controlFile: -3}

case $controlType in

	".xz")
		tarFlag="J"
		;;

	".gz")
		tarFlag="z"
		;;

	*)
		echo "unknown control format \"${controlType}\". Hint: add a case here to handle it.";
		exit 1;
		;;

esac


# Extract the debian control archive

mkdir $controlWorkdir
cd $controlWorkdir

tar "-x${tarFlag}f" "${workdir}/${controlFile}"

# Fix the dependency

sed s/libappindicator3-1/libayatana-appindicator3-1/g control > control.new

# Repackage the control archive

mv control.new control
tar "-c${tarFlag}f" $controlFile *
mv $controlFile "${workdir}/${controlFile}"

# Repackage the debian package

cd $workdir
ar rcs $targetName debian-binary $controlFile data.tar.*

# Make a new copy of the package

mv $targetName $target
echo created: $targetName

Debian 11 deprecated the libappindicator3-1 library and replaced it with libayatana-appindicator3-1. However, a number of vendor-provided deb packages like Discord, Slack, and Lens still reference libappindicator3-1. This script unpacks a .deb package, rewrites the dependency to the new, compatible libayatana-appindicator3-1 library, and repackages the debian package for you to install.