Comparisons with Debian
I'm curious about some of your descriptions here:
> the Calamares cross-distro installer, which is more flexible than Debian's approach
In Debian we have Calamares on our live media too. It's absolutely *not* more flexible than the Debian installer, but it can make really simple installations easy for people without complex needs. If you want more control over various bits of the installation (e.g. partitioning or which packages are installed) I'd absolutely recommend using Debian installer options like the netinst media instead.
> We installed Debian 12.11 for comparison, and it's definitely a bit less ready for use. You need a separate user account for root and the sudo command doesn't work by default.
If you read the text on screen whan you get to account setup, it's easy to get sudo working as you seem to prefer. Just don't supply a password for root and that's what will happen.
I'm also really surprised that you obsess so much about disk usage here. For a full-fledged desktop distro, 10GB of disk space is *really* not much. In the grand scheme of things, it's lost in the noise on modern hardware...
For the record: we're really very happy to see derivatives base themselves on Debian's work and spend time on things they care about, e.g. tweaking package selections and providing a differently focused experience for end users. Free Software is great for this!