Since Android is built on top of the Linux kernel, Android device makers have to provide, upon customer request, the source code for any Linux kernel binaries that ship on their devices. That includes not only the release date software but also any subsequent updates to the kernel. Chinese smartphone maker Xiaomi started rolling out global beta Android 9 Pie updates for the Xiaomi Mi 6 and Xiaomi Mi Mix 2 earlier this year, and now they've released the updated kernel source code for both devices. Unlike those two devices, the Red Magic 3 by Nubia is a recent addition to the smartphone scene, and it's only had one update since release. However, the kernel source code for this device has also been released.

Red Magic 3 Forums   Xiaomi Mi 6 Forums  Xiaomi Mi Mix 2 Forums

Both Xiaomi devices already have healthy custom development communities on our forums. The team behind LineageOS, for example, recently pushed official LineageOS 16 builds for both devices. Nubia's latest Red Magic gaming phone, on the other hand, is far too new to have any relevant custom development for it, but given its price, ease-of-unlocking, and now kernel source code availability, that might change in the future. With the kernel source code, independent developers can start building AOSP-based custom ROMs, TWRP, or custom kernels for the Red Magic 3.

Red Magic 3 Kernel Sources (NX629J & NX629J_INT)   Xiaomi Mi 6/Mi Mix 2 Kernel Sources

The Mi 6 and Mi Mix 2's kernel source code is available under the same tree, sagit-p-oss, where sagit is the code-name for the Mi 6. The Red Magic's code-name is NX629J, and Nubia has a separate tree for the international variant.