How do I find out more information about a pending software update? On my MacBook Air (13-inch, 2017) with macOS 10.15.4 (19E287), I am shown a software update that I cannot seem to install and that I want to know more about. 

How can I find out more information about such a pending software update and eventually install it?

Here is a GIF animation for further context: https://imgur.com/nm6YwY8
From the provided result, the Security update "061-90745" is an update still trying to be installed for Mojave! 



Clear the old update with defaults delete com.apple.preferences.softwareupdate LatestMajorOSSeenByUserBundleIdentifier &amp;&amp; softwareupdate --list

It removes the old incompatible string then refreshes the list from Apple

Congrats on the move to Catalina!