I want to learn about Linux. I saw FreeBSD have Handbook which is awesome, is there such a project for Linux?
Currently im using OpenSuse. I looked at their docs, but found nothing similiar.
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An Introduction to Linux from the Linux Documentation Project may be what you are looking for. Various distributions also have distribution specific documentation such as the Debian Documentation. For openSUSE, I would start with the Documentation Portal.
Documentation for Linux is extensive and covers a lot of areas. There are many documents targeted for specific user groups such as users migrating from Windows.