I'm upgrading an instance of Portal for ArcGIS 10.8 to Portal for ArcGIS 10.8.1. It's been going on 3 hours and the installation is still not completed. I can see in Task Manager that there are some processes still working, such as OpenJDK Platform binary and Windows installer (32 bit). At various points the Portal for ArcGIS 10.8.1 Setup wizard has shown activity in the status bar, but it hasn't shown anything except Status: and an empty progress bar for at least 1/2 hour.
I've disabled Windows Defender real-time protection as I've seen it slow down installations significantly in the past.