If you use Snap, Flatpak or Appimage, you need to only install ffmpeg if you want to use Similar Videos tool.

For Czkawka GUI the lowest supported version of GTK is 3.24 which is the only required dependency(of course on Ubuntu, different distributions will probably require a little different set of dependences).
In app exists Similar Video tool which require FFmpeg to work, but is completely optional and without it, only warning would be printed when trying to use this tool without installed ffmpeg.
Broken files finder by default don't check for music files, but it is possible to enable this feature and that require to have alsa lib installed(on Ubuntu this is libasound2-dev package)

Warning Main Czkawka GUI dependency - GTK 4 is only available on newer systems like e.g. Ubuntu 22.04, so if you have problems with running app on older systems, you may like to use older Czkawka versions, upgrade OS or install flatpak package which use its own set of dependencies.

sudo apt install libgtk-4-dev ffmpeg

sudo yum install gtk4-devel glib2-devel
sudo dnf -y install https://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-$(rpm -E %fedora).noarch.rpm
sudo dnf -y install https://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-$(rpm -E %fedora).noarch.rpm
sudo dnf -y install ffmpeg

sudo xbps-install gcc pkg-config ffmpeg

Currently, you need to manually install GTK 4 libraries, FFmpeg and the Adwaita theme, because they are dynamically loaded from the OS.
One very straight-forward way to do this is by using Homebrew.
Installation in the terminal:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
brew install gtk4 adwaita-icon-theme ffmpeg librsvg libheif

After that, go to the location where you downloaded Czkawka and add the executable permission to this file.

chmod +x mac_czkawka_gui

At the end execute it:

./mac_czkawka_gui

Warning
Prebuilt binaries are available only for x86_64, so if you use ARM machine like e.g. Mac M1, you need to compile manually app.

There is also a way to use x86_64 binaries on ARM, but this requires to install special version of required libraries probably via:

arch -x86_64 /usr/local/bin/brew install gtk4 adwaita-icon-theme ffmpeg librsvg libheif

Sadly this doesn't work for all users, so feel free to update this part of documentation(look at qarmin#689 and qarmin#637 for more info)

By default, all needed libraries are bundled with the app, inside windows_czkawka_gui.zip, but if you compile the app or just move czkawka_gui.exe, then you will need to install the GTK 4 runtime from here.

FFmpeg to be able to use Similar Videos, you can download and install from this link.

Ready-to-go executables for Linux, Windows and macOS are available here.
If the app does not run when clicking the launcher, run it through a terminal.
You don't need to have any additional libraries for CLI Czkawka.

Artifacts from each commit can be downloaded here

Appimage files are available in release page - GitHub releases
Available are 2 versions of Appimage:

• default - which bundle gtk theme
• alternative - which don't include any gtk specific libraries

The easiest method to install Czkawka is using the cargo command. To compile it, you need to get all the requirements from the compilation section.

cargo install czkawka_gui
cargo install czkawka_cli

You can update the package with the same command.

sudo snap install czkawka

By default, Snap can only access the files in your home directory. You have to allow Czkawka access to all the drives:

sudo snap connect czkawka:removable-media

The Snap store entry can be found here.

Fresh builds are available in edge branch, but they may be a little unstable.

flatpak install flathub com.github.qarmin.czkawka

Flathub page with Czkawka can be found here

Unofficial packages, which may not always provide the latest version of Czkawka.

sudo add-apt-repository ppa:xtradeb/apps
sudo apt-get update
sudo apt-get install czkawka

alternatively you can use instruction from this xtradeb site

Czkawka is also available in Arch Linux's AUR from which it can be easily installed.

yay -Syu czkawka-gui
yay -Syu czkawka-cli

or

yay -Syu czkawka-gui-bin
yay -Syu czkawka-cli-bin

Packages info

Czkawka docker image is available here

Windows Chocolatey binaries are available here