Based on our record, iOS 11 icons: Glyphs seems to be more popular. It has been mentiond 3 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
I downloaded the icons I needed from here. They are from no particular icon pack. I just selected the icons which I felt would fit in well with the theme I was going for and then edited them onto the wallpaper background images on my computer. It’s a tedious process but it becomes easy once you get used to it and the result is worth it ;). Source: over 2 years ago
Icons 8 (Free but sometimes they charge for full Res). Source: almost 3 years ago
Https://icons8.com/icons/ios You can use them by putting this link "https://img.icons8.com/ios/250/000000/icon.png" and just replace the word icon with the name of the icon (with spaces with replaced by a dash). Source: about 3 years ago
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iOS icons converter - SVG -> PNGs for all app icon sizes, for free.