Status: still working on math/sage (See D24195).
ECL (i.e. ports/lang/ecl) is an important piece of SageMath, but I have not been able to build sage/math with the existing port, unless applying heavy patches.
Furthermore, ECL is about to release v20.4.24, and SageMath will keep using 16.1.x for some time.
It's why it's better to repocopy lang/ecl to a special port, lang/ecl-sage, with the required patches.