One fact I was not completely aware about: Even if you have updated your Android device with a Custom ROM (e.g. Lineage/Cyanogen) to a newer Android Version you

One fact I was not completely aware about: Even if you have updated your Android device with a Custom ROM (e.g. Lineage/Cyanogen) to a newer Android Version you most likely still have an old Kernel. So yes, I am very happy that I can still run Android 7.1.2 on my 5 year old S3, but at the same time it runs on a 3.0 Linux kernel which was originally release in July 2011. As far as I know, that is because some drivers (e.g. the graphics driver) are closed source and are only available as binaries. Therefore, they were never properly integrated into the Linux kernel source and when the kernel changes nobody cares about them. Yes, I know about the discussion about stable ABIs, but even with a stable ABI, I would still be stuck with an outdated buggy graphics drivers, because the kernel developers only care about source they can access. To sum it up: I would like to have a product which does not only have an up-to-date userland software, but also a more or less current kernel.