Some changes were made to MoK Manager recently. It is no longer possible to boot in MoK unless we boot directly into (F12) the Kubuntu ee installer (not really a bug when knowing it):

Code:
sudo mokutil  --disable-validation
sudo mokutil  --enable-validation
In TW, continue boot to enroll key is not responding correctly, the Kernel won't compile for -rc3,4 and 5. In our many attempts to find a solution, in our last fresh install of 20190815 snapshot, we click ESC and miraculously -rc5 compiled properly.

Enroll key option was not shown, only as usual, continue boot. This option did not work in the previous 3 weeks. Apart booting in the KDE ee installer, there was no issues with the Kernel ppa = Stable (debian packages).

In between there was a Grub update, which is never a good news with secure boot enabled. Thanks in advance for considering a more durable solution, because secure boot is also in bad shape.

Mainline Kernel the Tumbleweed way (1):

Code:
rpm -qa | grep -i  kernel
kernel-firmware-radeon-20190712-276.1.noarch
kernel-devel-5.3.rc5-1.1.gcadbe00.noarch
kernel-syms-5.3.rc5-1.1.gcadbe00.x86_64
kernel-source-5.3.rc5-1.1.gcadbe00.noarch
patterns-devel-base-devel_kernel-20170319-8.4.x86_64
kernel-macros-5.3.rc5-1.1.gcadbe00.noarch
kernel-firmware-amdgpu-20190712-276.1.noarch
kernel-default-5.3.rc5-1.1.gcadbe00.x86_64
kernel-default-devel-5.3.rc5-1.1.gcadbe00.x86_64
kernel-firmware-realtek-20190712-276.1.noarch
kernel-firmware-20190712-276.1.noarch
mokutil  --sb-state
SecureBoot enabled
All the best,