Hello,
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like Google keyboard
is too broad, do you mean create a keyboard like native android?
If you need to add some extra keys for text input, you can Google(Due to the policy, I cannot give thread to you directly): Adding custom buttons to iOS Keyboard in C# & Xamarin
If you want to create a simple custom keyboard, create a Custom Keyboard Extension is better, please Google: Custom Keyboard In Xamarin.iOS Nandhakumar wirte a blog about it.
Best Regards,
Leon Lu
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