Same issue here,
Neither the December update (KB5048667) nor the January one (KB5050009) will install.
At best they will download, sometimes even install to 100% but either it fails and tells you to try again or after restarting and a long "upgrade in progress" nothing really happens.
I have tried downloading the msu packages from catalog.update.microsoft. It did not work.
Am I supposed to reinstall Windows? I know that you can keep apps and files but I distrust that it will keep my entire settings and I am not in the mood of starting from zero again.
Please provide a solution different to reinstalling Windows.
Reinstall? As I understand - it will only keep Microsoft apps. If you have anything else that is installed locally with its data, you will have to reinstall the app and its data from a backup and hope you have the licence key and can re-register.