I tried to install the 1909 update since there are messages that my current version 1803 will be out of support.
It doesn't work with Windows Update nor with the Windows 10 Update-Assistent.
I've tried the top 40 google results but none of them works.
SetupDiag doesn't come with an error as far as I can see (last action is a success).
After the 2nd reboot I've must enter the bitlocker recovery key to continue.