Since a few other people also tried this, I thought it might be worth an extra thread to share experiences.
For inexperienced users: Updating the kernel might brick your kiwi. Don't try it without a reason.
The how-to for updating the kernel is found here:
https://elinux.org/Beagleboard:BeagleBoneBlack_Debian#Kernel_UpgradeKernel versions I found to be working:
LTS49: 4.9.147-ti-r121
Kernel versions which might cause problems:
LTS44: 4.4.155-ti-r155 (high system load prevents GPS from acquiring satellites, lagging webinterface, seems to be missing firmware)
LTS414: 4.14.108-ti-r108 (doesn't boot)
LTS419: 4.19.50-ti-r20 (does boot, but
doesn't work with kiwid)
