Hello Linvincible,
If I try the proposed Cumulative Update for Windows 10 Version 1903 for x64-based Systems (KB4577671) I always get 0x800f0831. Started on-line or from download (disconnected internet). It makes no difference.
If I try a full in-place Windows 10 install (from ISO file) I always get 0xC1900101 - 0x40017. But don't have any third party antivirus nor firewall. Even disabling the build-in defender, as someone suggested, makes no difference. It take one hour and then it reverts because of an error during second boot.
Whatever I try, there is no way to move forward.
dism gives errors but I'm not skilled enough to understand the log file, there are errors that seem to be tolerable and there are severe ones.
This system has had a clunky mechanical harddrive, that I replace with a SSD using cloning. I would be surprised that some files are still corrupt and hinder one way or the other the upgrades.
Many thanks already for taking some time in order to help me forward.