What software/open source program would you recomend? I have tried Spriter, but it is very unstable. Therefore Im looking for another program to use with Unreal Engine and the
Paper2D preset.
-I personally just use photoshop for it -> there I draw my 2d sprites + animate them (I preview the animation with the “gif tool”.
-Another program is Algodoo. There you could animate your 2d character - take a picture of some frames - export it - create alpha channel - import it into the UE4
-You could also create an animation in blender + use the steps from Algodoo 
PyxelEdit was great! Bought it and it feels alot easier than Photoshop. Photoshop feels kinda heavy for just pixelart.
Thanks for the tips 
I recommend Anime Studio debut. It is powerful animation software. It provides pre-made characters and content that help you to start animating straight away. It has vector-based, powerful, and enhanced drawing tools give you authority to manipulate the art to give it the desired look and feel.