[neuromute]

Three animation tools (not strictly SVG-related) that spring to mind:

Pencil 2D

Synfig Studio

OpenToonz (used by Studio Ghibli, no less!)

If you want 3D, then Blender is a fantastic open source tool.

[buovjaga]

Synfig now includes a Lottie exporter: https://www.synfig.org/2019/12/27/whats-coming-to-synfig-1-4...

It is in the 1.3.12 release.

There is also this new tool called enve (Linux only): https://maurycyliebner.github.io/