Hi 
@jhowarth 
In order to install SecUpd2020-002Mojave, you must expand the .pkg file and then modify the "distribution" file.
Like this:
Move "SecUpd2020-002Mojave.pkg" file to the desktop
Open Terminal and writes this:
	
	
Press enter
	
	
	
		Code:
	
	
		pkgutil --expand SecUpd2020-002Mojave.pkg NewFolder
	 
 Press enter
Wait a few minutes
Go to the "NewFolder" folder created on your desktop and open the "Distribution" file with a text editor
Add: return true;
at the end of this line: 
function InstallationCheck(prefix) {
Like this: 
function InstallationCheck(prefix) {return true;
Add: return true;
at the end of this line: 
function VolumeCheck(prefix) {
Like this: 
function VolumeCheck(prefix) {return true;
Save the file
If you have not closed the terminal, write or simply copy this:
	
	
	
		Code:
	
	
		pkgutil --flatten NewFolder SecUpd2020-002MojaveModified.pkg
	 
 Press enter and wait a few minutes for the package to re-create
But if you closed the terminal, re-open it and writes this:
	
	
Press enter
	
	
	
		Code:
	
	
		pkgutil --flatten NewFolder SecUpd2020-002MojaveModified.pkg
	 
 Press enter and wait a few minutes for the package to re-create
Once the operation is completed, launch the file "SecUpd2020-002MojaveModified.pkg" The message "This software is not supported on your system" should no longer appear and the update should install.
AFTER INSTALLATION YOU MUST RESTART ON THE USB KEY AND RE-APPLY THE POST-INSTALL PATCH WITH CACHE REBUILD OTHERWISE MOJAVE WILL NOT START
Be careful if you have several OS on more disks/partitions in your mac because these modifications make it possible to install this update on any OS disk/partition.
AT THE BEGINNING OF THE INSTALLATION BE CAREFUL TO CHOOSE THE DISK/PARTITION OF MOJAVE AND NO OTHER.