Final cut pro unexpectedly quit - cannot open the app - crashing while starting

The FCP crash log shows thread 0 crashed due to an invalid memory reference from the class AVCaptureDevice. That in turn was likely caused by the 3rd-party plugin com.kinoni.EpocCamPlugIn (3.4.1rc2), and RelayCam.plugin.

Those plugins were within the address space of FCP, so any bug in those can crash FCP.

I suggest all 3rd-party A/V software be removed as a troubleshooting step. Also check for any kernel extensions. In general Apple has deprecated 3rd-party kernel extensions for years due to reliability and security issues. They have strongly recommended developers instead use the system extension API. The following terminal commands will check for presence of 3rd-party kernel extensions:

MacOS versions before Big Sur:

kextstat | grep -v com.apple

On Big Sur and later, the command is:

kmutil inspect | grep -v com.apple

In addition to Tom's request for an etrecheck report to see if there's something going on with your Mac, you can also try launching FCP and immediately pressing the option key. This will prevent it from automatically opening any libraries and ask you what you want to do. Do you get to the open/new dialog?

I notice a couple things from the etrecheck report:

Malware Detected:

[Loaded] ai.electric.osquery.unenroll.plist (Malware - installed 2023-03-15)
    Executable: /etc/osquery/osquery_unenrollment_script.sh

Google keystone software:

[Loaded] com.google.keystone.agent.plist (Google LLC - installed 2022-10-26)
    Command: ~/Library/Google/GoogleSoftwareUpdate/GoogleSoftwareUpdate.bundle/Contents/Resources/GoogleSoftwareUpdateAgent.app/Contents/MacOS/GoogleSoftwareUpdateAgent -runMode ifneeded

  [Loaded] com.google.keystone.xpcservice.plist (Google LLC - installed 2022-10-26)

Follow the instructions at https://chromeisbad.com on how to completely remove Google's software. Simply trashing Chrome.app is not enough. Their keystone software breaks the video toolbox and can damage the ProApps. Once all traces have been removed, move FCP to the trash (do not empty it) and re-download a fresh copy from the AppStore.

Finally, run the Malwarebytes application on demand only, don't run it constantly in the background.

Please post an EtreCheck report https://etrecheck.com giving the application Full Disk Access in Privacy & Security System Settings. Copy the report and use the Add Text button to paste the result into reply box. 

Everything's crashing.

First, do a complete uninstall of Chrome.

Do a complete uninstall of Chrome as explained here

https://support.google.com/chrome/answer/95319?co=GENIE.Platform%3DDesktop&hl=en

1. Right-click Chrome in the Dock and select Quit.
2. Open Finder.and go to the folder containing the Google Chrome application, usually the Applications folder
3. Drag Google Chrome to the Trash.

• In the Finder at the top of the screen, click Go>Go to Folder.

• Enter ~/Library/Application Support/Google/Chrome and click Go.
  • 
    
  • Select the Chrome folder, and drag it to the Trash.

1) Drag the application to the trash and empty it

2) Drag the following to the trash as well:

/Library/LaunchAgents/com.google.keystone.agent.plist

/Library/LaunchAgents/com.google.keystone.xpcservice.plist

/Library/LaunchDaemons/com.google.keystone.daemon.plist

After removing Chrome, reinstall FCP from the App Store.

Next, switch off MalwareBytes and remove from login items if it's there.

Then, make a new admin user, reboot, log into the new user, and test the application.