>The Android kernel source code is in git: https://android.googlesource.com/kernel/common/

That's the mainline kernel. Actual devices use various LTS kernels, for instance the pixel 9a uses kernel 6.1[1], which was hasn't been updated in a year[2]

[1] https://wiki.lineageos.org/devices/tegu/

[2] https://android.googlesource.com/device/google/tegu-kernels/...