I think I stepped on someone else's post, so I am re-posting this. (I originally replied to the post on 10/16/2020, so the date sequence might be a little out of context.)
"2020-10 Cumulative Update for Windows 10 Version 2004 for x64-based Systems (KB4579311)Failed to install on 10/15/2020 - 0x800f0988". It hung at 0%, 11%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, jumped to 73%, then stated an error message and wanted me to try again. It was late evening 10/15/2020, so I shut down. I booted up this morning and it looks like the same sequence is occurring.
Same problem this morning. It went from 73% to 100% then an error occurred.
Last checked: Yesterday, 10:26 PM
There were some problems installing updates, but we'll try again later. If you keep seeing this and want to search the web or contact support for information, this may help: (0x800f0988)"
KB4579311 failed to install thru Windows update 3, actually 4, times, so I went to the Microsoft Download Center, picked the proper download and tried to install from there. That also failed. I also have not seen the Malicious Software removal tool for October.
10/17/2020: It is trying to install again this morning with the same apparent problem, so I paused it for now.
Windows 10 Pro
OS Build 19041.508