If been, looking my self from time to time to find an alternative to after effects, recently got rid of my adobe subscription - but still could not replace that specific piece of software. Maybe someone has some good experience?
I’ve seen people use Blender for 2d animation, it’s become kind of a “multi tool”, that should let you integrate it with any of the other features.
For raw 2d animation, Krita has some support, there is also Synfig and OpenToonz. For simple stuff, Gimp works in a pinch.
Blender is nice but last time I checked it was not well optimised for 2d animation, motion graphics. But maybe it’s time to give it another go - I think it’s one of the best open source projects ever. The other one you mentioned lack in the motion design department. Gimp still gives me nightmares.
I use it for basic 2D animation - overlays for videos (captions, title sequences, etc.) and animated diagrams - it works really well when you get used to it (mastering the curves editor is essential!). If you’re going to composite what you do onto video outside of Blender (I use Resolve) you need to export as an image sequence in a format that supports transparency (e.g. png).
For more complex 2D work, Marco Bucci has an interesting three-part series here (the third part goes over animation specifically).
