- I'm the designer of IconJar and we intentionally settled for one platform to have more control over the performance of the app. We do know Windows people are experiencing issues with managing their icon sets too, though. I usually recommend Nucleo as they also support our .iconjar files.
- Streamline is the world's largest icon library and has been my go-to for icons for the last few months. The icon library is very well organized, and is frequently updated with new icons. In addition, Streamline has a simple web viewer which can help you navigate their library, and have different weights so you can pick the icon just right for your project.