I wanted to replace the default kernel provided by the Raspberry Pi Foundation (raspberrypi-kernel) with one of the Raspbian kernels (linux-image-rpi*). I noticed that the DTBs and overlays are gone (/boot/overlay and /boot/*.dtb). Without them, the device does not boot.
My investigation has revealed that those things are indeed included in the raspberrypi-kernel package. That means, they are actually a part of the kernel. So why are they not in the Raspian kernels? Maybe there is another package I couldn't find that those kernels for some reason do not depend on?
There is also raspberrypi-bootloader-nokernel, and it seems that it includes those things - which explains the difference between "-nokernel" and the normal bootloader. However, this package seems to be outdated (March 2018), and also for some reason libraspberrypi depends on the "normal" bootloader and wants to remove this one. I understand that libraspberrypi is provided by the Foundation and not by Raspbian, but surely there must be some reason for this that I overlooked?..