For Super User you will find it at https://superuser.com/help/on-topic

For Unix & Linux you will find it at https://unix.stackexchange.com/help/on-topic

For any site just click the Help (?) button near top right of its banner:

and choose Help Cemter then What topics can I ask about here?

For Super User you will find it at https://superuser.com/help/on-topic

For Unix & Linux you will find it at https://unix.stackexchange.com/help/on-topic

For any site just click the Help (?) button near top right of its banner:

and choose Help Center then What topics can I ask about here?