Since https://github.com/python/cpython/pull/23122, there is PyModule_AddObjectRef doesn't steal a reference.
PyModule_AddObject is discouraged in the docs, but not formally deprecated. (As Stefan notes, the leaks are single references in case of a module initialization failure -- the cost of using the API incorrectly is very small; requiring everyone to change their code because it was possible to misuse it is overkill.)

See https://docs.python.org/3.10/c-api/module.html#c.PyModule_AddObjectRef

I think this is enough to close the issue.