Arch Linux made declarative, immutable and atomic. With Android app support and Fedora, Debian, CentOS Stream and Ubuntu containers available, as well as system packages/DEs/kernels from Arch Linux and the AUR.
This project allows for the creation of new Ubuntu-based distributions; it was formerly used by Ubuntu Unity, Ubuntu Cinnamon and Ubuntu Web Remix. Repo:
https://gitlab.com/ubuntu-unity/ubuntu-remixes