What are some alternatives?
When comparing Synfig Studio and OpenToonz, you can also consider the following products
Adobe Animate - Adobe Animate is a Flash, vector animation software.
Pencil2D - Pencil2D is an opensource animation/drawing software for Mac OS X, Windows, and Linux, based on old...
Spine - Spine is 2D animation software designed specifically for software and game development.
TVPaint Animation - TVP Animation is the leading paperless drawing and animation tool, able to imitate traditional 2D animation.
Pencil - Pencil is an animation/drawing software for Mac OS X, Windows, and Linux.
Toon Boom Harmony - Production-ready animation software for every artist, in any style.