From my so far limited experience of playing around with it for 30 minutes in a QEMU KVM, it does use the apt package manager but a quick look at /etc/apt/sources.list tells that they use their own repositories. Looking through the repositories of what they have to offer it seems that they aren’t just mirrors from another distro but actually maintain their own packages and port some Ubuntu packages. A look through their Kernel Config zcat /proc/config.gz tells that they compile their own custom Kernel as well. Also it doesn’t use snap at all, but they do offer it in their repositories. And for some reason there is dockerd/containerd pre-installed and pre-configured on the base System. My guess would be that they use docker for the Mobile apps, but I can’t verify this right now since every time I try to install a Mobile app from the Software Store it tells me that I can’t run a VM inside a VM. And unfortunately I don’t have some spare Hardware to test at hand atm.

To answer your question; It seems like an independent distro utilizing the apt package manager and porting some Ubuntu packages. But I can’t say for sure, since all of the documentation on their git repositories is written in mandarin.