Pencil is described as 'animation/drawing software for Mac OS X, Windows, and Linux. It lets you create traditional hand-drawn animation (cartoon) using both bitmap and vector graphics' and is a popular app in the Photos & Graphics category. There are more than 25 alternatives to Pencil for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and Android. The best alternative is OpenToonz, which is both free and Open Source. Other great apps like Pencil are Wick Editor (Free, Open Source), Synfig Studio (Free, Open Source), Pencil2D (Free, Open Source) and Karbon (Free, Open Source).
The Wick Editor is a free and open-source tool for creating games, animations, and everything in-between. It's designed to be the most accessible tool for creating multimedia projects on the web. Your creations can run on any device with a web browser - that means mobile too.
Synfig is a free and open-source, industrial-strength, vector-based 2D animation app designed for producing feature-film animations. It eliminates the need to create animations frame by frame. It is available for Windows, Linux, and macOS.
Pencil2D is an opensource animation/drawing software for Mac OS X, Windows, and Linux, based on old Pencil software. It lets you create traditional hand-drawn animation (cartoon) using both bitmap and vector graphics.
Pencil2D vs Pencil opinions
Almost everyone thinks Pencil2D is a great alternative to Pencil.
Karbon, component of Calligra Suite , is the scalable vector drawing application in KDE. It allows artists to create complex drawings without losing image quality when zooming in on, or resizing the drawing.
Animation Desk is a perfect tool for animating, storyboarding, and sketching. It’s an app Loved by professional and amateur animators, Youtubers, and many art lovers. Draw you frame-to-frame animation from scratch, or create animations upon videos, images, PSD layers.