Install Godot 3 stable or 4 beta, rc or stable and create desktop entry for Linux

Godot template.desktop

[Desktop Entry]
Name=Godot Engine $VERSION $CHANNEL
GenericName=Libre game engine
Comment=Multi-platform 2D and 3D game engine with a feature-rich editor
Exec=godot$VERSION_$CHANNEL %f
Icon=$HOME/.local/share/applications/godot.png
Terminal=false
Type=Application
MimeType=application/x-godot-project;
Categories=Development;IDE;
Name[en_US]=Godot $VERSION $CHANNEL.desktop

install_godot_and_create_desktop_entry.sh

#!/usr/bin/env bash

# Gist: https://gist.github.com/hsandt/113d3c6698a54e378d44b5024140c2a0

usage() {
  echo "Usage: install_godot_and_create_desktop_entry.sh version channel

Install a non-mono version of Godot for Linux.

Requirements:
- perl installed
- \"Godot template.desktop\" placed in the same directory as this script
- Godot icon placed at ~/.local/share/applications/godot.png

ARGUMENTS
  version    Version of godot to download. Do not include channel like 'beta' here. Ex: '4.0.1'.
  channel    Channel of godot to download, including number. Ex: 'beta14', 'rc1', 'stable'
"
}

if ! [[ $# -eq 2 ]]; then
  echo "Wrong number of positional arguments: found $#, expected 2."
  echo "Passed positional arguments: $@"
  usage
  exit 1
fi

version="$1"
channel="$2"
shift 2

parent_dir_path="$(dirname "$0")"

if [[ "$version" == 3* ]]; then
  # Godot 3 was naming "X11" the Linux build
  linux_suffix="x11.64"
else
  linux_suffix="linux.x86_64"
fi

godot_bin_name="Godot_v${version}-${channel}_${linux_suffix}"
godot_bin_zip="${godot_bin_name}.zip"

# Remove existing archive if any (in case it was previously incorrectly downloaded)
rm -f "$godot_bin_zip"

if [[ "$channel" == "stable"* ]]; then
  # Stable releases are on GitHub
  download_url="https://github.com/godotengine/godot/releases/download/${version}-${channel}/Godot_v${version}-stable_${linux_suffix}.zip"
else
  # Release candidates are on Tux Family
  download_url="https://downloads.tuxfamily.org/godotengine/${version}/${channel}/${godot_bin_zip}"
fi

# Download archive for passed version in current folder
wget "$download_url"

# Unzip it
unzip "$godot_bin_zip"

# Remove archive to clean up current folder
rm "$godot_bin_zip"

install_folder="${HOME}/Applications/Game Engines/Godot"
install_path="${install_folder}/${godot_bin_name}"
symlink_path="${HOME}/.local/bin/godot${version}_${channel}"

# It should have extracted a file named "$godot_bin_name", so move it to the target folder (overwrites any existing file)
mv "$godot_bin_name" "$install_folder"

echo "Installed in ${install_path}"

# Create symbolic link for terminal and future Desktop entry (overwrites any existing link)
ln -sf "${install_path}" "${symlink_path}"

echo "Created symbolic link in ${symlink_path}"

# Create Desktop entry from template (overwrites any existing file)
desktop_entry_path="${HOME}/.local/share/applications/Godot ${version} ${channel}.desktop"
cp "${parent_dir_path}/Godot template.desktop" "$desktop_entry_path"

# https://stackoverflow.com/questions/6994947/how-to-replace-a-string-in-an-existing-file-in-perl
perl -pi -e "s/\\\$VERSION/${version}/g" "$desktop_entry_path"
perl -pi -e "s/\\\$CHANNEL/${channel}/g" "$desktop_entry_path"

# https://stackoverflow.com/questions/26080096/installed-desktop-file-to-have-users-home-directory-path-inserted
# mind the comma separator since we deal with paths containing slashes
# we could also convert "~" but in this case, the template contains "$HOME"
# (which doesn't work per se, it needs path expansion)
perl -pi -e "s,\\\$HOME,${HOME},g" "$desktop_entry_path"

echo "Created desktop entry in ${desktop_entry_path}"

I also found another script that does a similar thing but is self-contained: https://gist.github.com/hieuns/ac4f117492771a690fa06cfa47b24714

It auto-downloads the icon svg from Wikimedia and embeds the .desktop template content in the same script.

However, it takes the Godot URL argument, making it more flexible but unable to retrieve the correct URL from version+channel automatically.

It may be worth merging both methods (download icon and deduce URL, possibly embed the template too) for a simple script the user can run without extra setup.