From Symantec Endpoint Protection 14.3 RU9, the SEP Linux Agent installation process will install the last supported version of the SEP Linux Agent on the target Linux operating system version.
All RU9 installation packages for SEP 14.3 RU9
All Linux distributions not supported on SEP 14.3 RU9
For the Linux Agent kernel supported for each Release Update. see https://techdocs.broadcom.com/us/en/symantec-security-software/endpoint-security-and-management/endpoint-security/sescloud/Release-Notes/supported-kernels-of-symantec-linux-agent-v133465487-d4155e7808.html
This is by design. Rather than blocking an installation for an unsupported version, the SEP Agent will be matched to the last supported version instead.
For information only.