Hi Thewizrd,
We appreciate you reaching out to us. We understand that you are getting a "Safari no longer supports this extension" message, even if there are no extensions installed in Safari.
First, let's update your device to macOS Ventura 13.0.1.
What's new in the updates for macOS Ventura - Apple Support
Update macOS on Mac - Apple Support
If the issue persists after the update, please check if you will experience the issue when signed in on a different user account.
This step will help in isolating the issue.
The article below can help if you do not have any other user account to test with.
Set up users, guests, and groups on Mac
If you are experiencing the issue when signed in on a different user account, please check if the issue persists while on safe mode.
Safe mode does a basic check of your startup disk, similar to using First Aid in Disk Utility.
Performing this step may help resolve the issue, or further isolate the issue.
Below is an article to help guide you through the process.
How to use safe mode on your Mac
Take care!