FingerPaint is a simple tool for Linux that allows drawing using the laptop’s touchpad. It supports all X11 desktop environments and GNOME with Wayland.
The most obvious use for this tool is to digitize your signature to sign PDF documents, but you can also use it to enter complex characters or to… doodle.
The application needs to run from the command line, in order to specify various parameters, but once you run it, a GUI is displayed which shows what you’re drawing on the laptop touchpad in real time.