You might be able to use C++11.
I just checked these docs 1, where it’s claiming:

The C++ frontend exposes a pure C++11 API that extends this underlying C++ codebase with tools required for machine learning training and inference.

so I’m unsure why the build instructions name C++14 as the required version.
Also the download 1 supports the Pre-cxx11 ABI and cxx11 ABI in case you want to download it without building.
These instructions 3 are also targeting a libtorch-only build. I haven’t used it in a while and am usually building libtorch as part of a complete source build.