Okay, I did that and checked the cbs.log and did something more, here's my changelog:
- replaced about a dozen .manifest-files in \Windows\WinSxS\Manifests which where definitely garbage (opened them with notepad++ and compared them to the content of a working Win10 installation)
- replaced that .mum-file (RestrictedCodecs?) along with its .cat-file in \Windows\Servicing\Packages that caused an error
- executed several runs of sfc.exe in between, each time there were less errors in it
- executed a dism /restorehealth which finished successfully this time telling me that everything has been repaired
- Windows update installed a few updates which required reboots, although I don't know which updates these were
- updated a few applications plus the Nvidia video driver (Libreoffice for example refused to start due to DLL-errors)
Then my last SFC.exe run told me that there were still a few corrupted files which could not be fixed, although it finished at 100%.
I turned off the PC, went to bed and the next run of sfc.exe told me that it found no integrity-errors at all. I guess that's the best message I got so far.
The log is attached to this message.
...but there are two things left I haven't investigated so far: I cannot open the system settings anymore. The window opens and closes right away.
I read that this is a well-known problem and could be linked to the file \Windows\ImmersiveControlPanel\Application.manifest but I don't have it and my other Win10 notebook does not have it, too.
When I right-click on the Windows background and choose "personalize", I get a error message from ms-settings
ersonalization-background that there is no app connected to this action.