Kext notarization was added in macOS 10.14.5.See About authorizing kernel extensions for Symantec Endpoint Protection for macOS 10.15. However, if you reinstall the operating system, you need to reauthorize the kernel extension.

If you have Symantec Endpoint Protection 14 and then upgrade to macOS 10.13, you don't need to reauthorize the kernel extension. If you uninstall and reinstall the client, you don't need to reauthorize the kernel extension. You only need to authorize the kernel extension once during the life of the computer's operating system. Neither Symantec Endpoint Protection nor the Mac operating system continue to remind you that you must do this. If you do not do it during the client installation, go to System Preferences > Security & Privacy, and click Allow. You are prompted during the client installation to do it if needed. As of macOS 10.13, you must authorize the Symantec Endpoint Protection kernel extension after installation for Symantec Endpoint Protection to fully function.Mac clients for Symantec Endpoint Protection Cloud do not support Mac OS X 10.11 (El Capitan).See Remove Symantec software for Mac using RemoveSymantecMacFiles. Remove legacy Symantec AntiVirus (SAV) for Mac installations before installing Symantec Endpoint Protection.Case-sensitive APFS volumes are not supported. As of version 12.1.2, SEP supports case-sensitivity in HFS volumes.PowerPC processors are not supported as of version 12.1.x.Neither Apple or Symantec support macOS 10.13.x or older.Apple M1 (M1 Pro/M1 Max) is only supported by SEP 14.3 RU2 and later.The 14.3 RU4 installer ships with the 14.3 RU3 Mac client. The SES Mac client is only supported on macOS 10.15.x and 11.x with the SES Mac agent build 14.3 RU1 and newer.The Symantec Endpoint Security (SES) client for Mac is cloud-based and managed by the Integrated Cyber Defense Manager (ICDM) web page.The SEP client for Mac is managed by a Symantec Endpoint Protection Manager (SEPM) on a Windows server.Note: Different product versions have specific system requirements. SEP 14.x Client for macOS/OS X Compatibility Chart

Mac os list of versions