There are dozens of Raspberry Pi Alternatives and they all seem to have the same goal. Provide better performance than the Raspberry Pi. This just tells you that none of these boardmakers understand what Raspberry Pi foundation stands for.
Raspberry Pi are cheap
Have loads of documentation to learn.
Is supported by several Linux distros.
Free forums and Raspberry Pi Mag for information and projects.
The competitors like Khadas have none of these features. Looking at their website, they're very eager to sell their board and cost twice as much as Raspberry Pi. But when I try to search for learning resources or documentation, they fall short of provide anything useful. Khadas VIM4 is not supported by Ubuntu at the moment due to driver issues. I don't have these issues with Raspberry Pi.