Trying to ignore the macOS Big Sur update (unsuccessfully)

IgnoreUpdates.m

#import <Foundation/Foundation.h>
#import <sysexits.h>

/*
 * Trying to bypass the fact that running `sudo /usr/sbin/softwareupdate --reset-ignored && sudo /usr/sbin/softwareupdate --ignore "macOS Big Sur"`
 * does not work anymore on macOS Mojave 10.14.6 (ignored updates is empty) by using the underlying SoftwareUpdate framework directly.
 * Unfortunately, this did not work as expected. The preference is written when this tool is run as root but opening the software update
 * preference pane still displays the macOS Big Sur update :-(
 *
 * References
 * - https://lapcatsoftware.com/articles/software-update.html
 * - https://apple.stackexchange.com/questions/406413/how-do-i-stop-big-sur-from-installing-on-my-computer
 */

int Run(NSArray *ignoreUpdates)
{
    NSString *softwareUpdatePath = @"/System/Library/PrivateFrameworks/SoftwareUpdate.framework";
    NSBundle *softwareUpdateBundle = [NSBundle bundleWithPath:softwareUpdatePath];
    NSError *error;
    BOOL loaded = [softwareUpdateBundle loadAndReturnError:&error];
    if (!loaded)
    {
        NSLog(@"Failed to load %@ \n%@", softwareUpdatePath, error ?: [NSString stringWithFormat:@"Make sure that %@ exists on disk", softwareUpdatePath]);
        return EX_SOFTWARE;
    }
    
    Class SUSharedPrefs = NSClassFromString(@"SUSharedPrefs");
    if (SUSharedPrefs == Nil)
    {
        NSLog(@"SUSharedPrefs class not found");
        return EX_SOFTWARE;
    }
    
    id sharedPrefManager = [SUSharedPrefs performSelector:@selector(sharedPrefManager)];
    if (sharedPrefManager == nil)
    {
        NSLog(@"sharedPrefManager is nil");
        return EX_SOFTWARE;
    }
    
    [sharedPrefManager performSelector:@selector(setInactiveProductLabels:) withObject:ignoreUpdates];
    
    NSArray *inactiveProductLabels = [sharedPrefManager performSelector:@selector(inactiveProductLabels)];
    if (inactiveProductLabels.count == 0)
    {
        NSLog(@"There are no ignored updates.");
    }
    else if (inactiveProductLabels.count == 1)
    {
        NSLog(@"Ignored update: %@", inactiveProductLabels[0]);
    }
    else
    {
        NSLog(@"Ignored updates: %@", @(inactiveProductLabels.count));
        for (id inactiveProductLabel in inactiveProductLabels)
        {
            NSLog(@"  * %@", inactiveProductLabel);
        }
    }
    
    BOOL success = [inactiveProductLabels isEqualToArray:ignoreUpdates];
    if (!success)
    {
        NSLog(@"Ignoring (%@) failed. Make sure to run this tool as root.", [ignoreUpdates componentsJoinedByString:@", "]);
    }
    
    NSString *softwareupdateCommand = @"/usr/sbin/softwareupdate --ignore";
    NSLog(@"Running %@", softwareupdateCommand);
    system(softwareupdateCommand.fileSystemRepresentation);
    
    return success ? EX_OK : EX_NOPERM;
}

int main(int argc, char *argv[])
{
    @autoreleasepool
    {
        @try
        {
            return Run(@[ @"macOS Big Sur" ]);
        }
        @catch (NSException *exception)
        {
            NSLog(@"An unexpected error occurred: %@", exception);
            return EX_SOFTWARE;
        }
    }
}