UI Testing Academy is a free resource that provides practical examples and helpful information about UI Testing for different platforms. You can find a live version of the project at ui-testing.academy.
The project is live. The amount of content will be increased. Right now, the project has information about general tips and recommendations which can be applied for all platforms, but more platform-specific information will be added soon.
If you want to see specific content, please feel free to crete an issue in this repository.