Libre office draw is wonderful, it can edit pdf docs at ease. It’s crazly powerful compared to paint 3d
draw.io - Online diagramming application
YouiDraw - Draw and Design Vector Graphics, Logo, Text, icon in the Cloud.
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.
DrawBerry - All the features of other vector editing applications such as Adobe Illustrator or Inkscape, in a...
Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.
formo.one - Create generative art from any kind of photo