All files are quarantined after OS upgrade, not just Apps

Thanks for your reply. I think you misunderstood. I can't even open a .png file. I don't believe this has anything to do with 32-bit vs 64-bit. I checked before I upgraded, and I only had a few 32-bit apps that I was no longer using.

This is the summary:

Major Issues

Battery failure

Your battery is reporting that it needs to be serviced.

Automatic updates disabled

Automatic updates are disabled. This computer is at risk of malware infection.

Security updates disabled

Security updates are disabled. This computer is at risk of malware infection.

Apple security disabled

Apple security software is disabled. This computer is at risk of malware infection.

Minor Issues

System extensions installed

This computer has system extensions installed. System extensions can be difficult to uninstall.

Heavy RAM usage

Apps are using a large amount of RAM.

Apps crashing

There have been numerous app crashes.

Clean up

There are orphan files that could be removed.

Unsigned files

There are unsigned software files installed. These files could be old, incompatible, and cause problems. They should be reviewed.

System modifications

There are a large number of system modifications running in the background.

Limited permissions

More information may be available with Full Disk Access.

Kernel extensions present

This computer has kernel extensions that may not work in the future.

Sharing enabled

This computer has sharing services enabled that could be a security risk.

Security

System

Gatekeeper

App Store and identified developers

System Integrity Protection

Enabled

Automatic Updates

Disabled

Security Updates

Disabled

Antivirus software

None!

Sharing Services

Remote Management

Enabled

Screen sharing

Enabled

Thanks, I'll consider that...