If a paid license isn't an option, these tools offer robust "forever free" tiers:
Miro offers 3 free editable boards with infinite canvas.
Finally, it is important to acknowledge that the developers of SmartDraw employ teams of engineers, designers, and support staff to create and maintain the product. The revenue from license keys funds the development of new features and ensures the software remains cutting-edge. When users bypass this payment, it undermines the ecosystem that creates the tool they rely on.