[boost] Support status for C++03 (std=c++03) in Boost [Version] on RHEL 9

Hello Boost Community, I am currently planning a large-scale migration of a legacy codebase from SourcePro Rogue Wave to Boost. Due to strict production requirements, we must maintain the -std=c++03 flag across environments: RedHat 9 (GCC 5.x) My Question: Is there any version of Boost, which can be considered the "Long Term Support" equivalent for C++03, for which Boost also release latest patch or security vulnerabilities or actively maintain that version? From older post/blogs, it seems Boost does not manage c++03 standard and provide support of latest standard of c++ only i.e. C++14 and so on. Thanks And Regards, Piyush