Natron - Open source and Free After FX alternative
Natron is a powerful Digital Compositor that can handle all of your 2D/2.5D needs. Its robust OIIO file formats and OpenFX architecture is what make Natron the most flexible open source compositor for the visual effects community.
It takes an hour or two to 'grok the flow' but once you do it's simple enough after that.
So far not as many plugins as after FX but that's to be expected. It handles video formats nicely. Allwing me to easiliy work with OBS studio.