Byzantium is supported, we aim to fix bugs and ensure it is up to date and secure. But because it is a rolling release it is updated frequently and that brings more instability. Amber is less frequently updated and software has had a longer testing cycle by users and in production. At some point, and this will be announced in the future, likely next year, Byzantium will become our “stable” distro. Amber will become “old stable” (or even deprecated) and we’ll have a new rolling release.