When I'm trying to export one of my folders as a catalog to external SSD drive Lightroom Classic 12 quits and says there was an unexpected error. When i export to my desktop it's exports ok. I have enabled full disc access for lightroom in system preferences.
Adobe Lightroom Classic 12 
OS Version: macOS 13.0 (22A380)
I am not able to replicate this error - moving to discussions.
It is possible this is related to Mac's OS Update. Are you running the Beta or the production version released yesterday? Lightroom Classic will be releasing an update shortly to deal with Ventura issue stragglers.
Would your issue be related to the issue in the link below, and if you were to create a catalog on an external hard drive with MACOS Ventura, would you not then run into the problem in the link below:
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I have checked this problem today after updating my Lightroom to 12.0.1 and now everything working fine.
Thank you Lightroom Team 🙂