Synfig Studio

About

Synfig Studio is a free and open-source 2D animation software, designed as powerful industrial-strength solution for creating film-quality animation using a vector and bitmap artwork. It eliminates the need to create animation frame-by frame, allowing you to produce 2D animation of a higher quality with fewer people and resources. Synfig Studio is available for Windows, Linux and MacOS.

https://synfig.org/

Installing

Debian/Ubuntu

Download the AppImage file from the website.
Left-click on the file and select properties. Navigate to permissions and check the box that says Allow executing file as program. Finally, run the file.

For more information see https://discourse.appimage.org/t/how-to-make-an-appimage-executable/80.

Windows

Download the .exe file from the website.
Run the file. A wizard will then guide you through the rest of the installation.

MacOS

Download the .dmg file from the website.
Drag the file into your applications directory, then run it.

If you get an error message like "can't be opened because it comes from a non identified developer", then do the following:

Locate the Synfig app in Finder (don’t use Launchpad to do this - Launchpad doesn't allow you to access the shortcut menu)
Control-click the app icon, choose "Open" from the shortcut menu.
Click Open.

The app is saved as an exception to your security settings, and you can open it in the future by double-clicking it just as you can any registered app.

NOTE

You can also grant an exception for a blocked app by clicking the “Open Anyway” button in the General pane of Security & Privacy preferences. This button is available for about an hour after you try to open the app. To open this pane, choose Apple menu > System Preferences, click Security & Privacy, then click General.

For more details please refer to this page