[BPI-P2 Pro] Debian Image Source code?

Where can I find the source code for the latest debian images? The product page for BPI-P2 Pro Banana Pi BPI-P2 Pro | BananaPi Docs says the source code is:

linux-5.10.110 kernel BSP Source code on github : GitHub - ArmSoM/armsom-p2pro-bsp

But the repo is older (hasn’t been updated in a year) than the latest debian image, which is dated 2024-05-24. More importantly, when I follow the instructions to install it on Ubuntu, I get errors when I try to build a full debian image.

Also, what is the purpose of the buildroot image?

Thanks for your help