The best alternatives to Iconic are Illustrio, Source Wireframe Kit, and silhoutteAC. If these 3 options don't work for you, we've listed a few more alternatives below.
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AssemblyAI— Speech-to-Text API with superhuman accuracy
Create effective prototypes that are convertible to the final design in a few minutes with the Source Wireframe Kit. It contains a high-quality collection of 537 pixel-perfect and thoughtfully created blocks for desktop and mobile combined into design system.