iXsystems put TrueNAS CORE into what it called a sustaining engineering phase back in 2024. Under this, the open source NAS operating system would only receive security and stability fixes, with new features going to the Linux-based SCALE branch instead. (…) It traces directly back through TrueNAS CORE to FreeNAS, and it’s built on the same foundation CORE always used: FreeBSD and OpenZFS. The current stable release is 15.0-U1.3, and it is aimed at TrueNAS CORE holdouts.