People reported challenges building V8 (whether upstream or the Node.js variant) on s390x with z13 support. I don't know if it was discussed on the porters mailing list because it's not public: https://groups.google.com/g/v8-s390-ports
Elsewhere, some people interpreted https://github.com/google/highway/issues/1895 as meaning that Highway code does not work on z13 at all.