erikkfi, macpro_mid2014 guided you correctly. It also looks like you have now since found a reference for this in troubleshooting. In plain terms, I'm also going to outline it here for others:
Problem: You can only startup when the Installer USB is inserted
Explanation: The OCLP Ventura Installer USB contains the EFI you need to boot and your internal SSD does not, thus giving you the 🚫 prohibitory sign without the OCLP Ventura Installer USB present.
What Happened? Typically, the OCLP Ventura USB Installer should automatically install the OCLP EFI on your internal SSD during the OS install process unless it has changed in version releases? This way, you don't require the USB to always be inserted. If this did not happen, others could likely explain better than me the reasons why. Nonetheless, you can always install it manually yourself:
Resolution: To save you going the route of a complete reinstall, you'll need to boot into a macOS system (same system, external disk/USB or different system) where you can access the v0.5.2 OpenCore-Patcher App. Once done, follow these steps to get the v0.5.2 EFI installed on your internal SSD:
1. Launch OpenCore-Patcher
2. Verify your system is correctly listed next to Model at the top of window. Assuming so, I recommend going with the Defaults automatically selected for your system by OCLP.
2A. (Optional/Expert). If you know what you are modifying and why, you can select the Settings button, make appropriate changes, and select Return to Main Menu. Again, know what you are doing here or you are only possibly contributing to the problem.
3. Select Build and Install OpenCore
4. Important! When a window prompts you for the correct disk to install MAKE SURE you know the device string for your internal SSD. For this reason, I recommend either before or during this part you open macOS terminal and type 'diskutil list' so you can see all disks listed, confirm your internal SSD device string, and then know you are clicking the appropriate selection for the EFI installation. Another good indicator is knowing the size of your drive and not having other, unnecessary drives connected during this process.
5. OpenCore-Patcher will do its thing, install the EFI on your internal SSD, and should prompt you to Reboot. If not, I recommend ejecting your Installer USB and Rebooting.
Expected Behavior: Based upon default settings, system should reboot and briefly display EFI and your internal SSD and then automatically boot.
Alternate Try 1 (if needed): If for some reason it doesn't, you can try to reboot again and hold down 'Option' key, then select 'EFI', then select your internal SSD. Then system should automatically boot into Ventura.
Alternate Try 2 (if needed): If you are still experiencing problems, you need to reset you Parameter RAM (PRAM) by first Shutting Down-PowerOn or Restarting computer and then immediately at boot chime hold down Command-Option-P-R AND KEEP HOLDING THOSE KEYS until you hear at least 3 boot chimes then release keys. This is going to take a minute, be patient. Then after 3rd chime, you should get the Boot Screen as in first line of Expected Behavior.
If this does not work, unfortunately I would recommend rebuilding your OCLP Installer USB again and reinstall, unless others have recommendations for your particular scenario. Hopefully, this step-thru helps you or others experiencing similar behavior to begin experiencing the amazing OpenCore-Patcher the developers have created. It's really unbelievable what has been accomplished by this development team for the Mac Community!
