You should use the newest version of SEP, currently 14.3_RU8 (14.3.8151.8000). We stopped developing your version around RHEL 8.2. You don't need an internet connection or a repository; use the SEP Linux Packager tool on another machine that does have an internet connection and create an offline LinuxInstaller package. Installation example is given at bottom of linked page:
If the system is in an isolated environment without access to the Internet, run the installer with following option. This would install SEP Linux 14.3 RU8 without checking for software update.
/root/pkg/LinuxInstaller.rhel7.sep14.3ru8.<timestamp> -- -g