@leszek Neptune 8 is shaping up nicely and the way I see it, it's going to be the best Neptune ever made. Congratulations! You've been doing an amazingly good job.

Now, if I may, I'd like to make some suggestions.
It would be nice and useful if you included (at least some of) the following software into the ISO:

firewalld
firewall-applet
sweeper
pppoe (has nothing to do with dial-up; the pppoe protocol is currently used by a number of ISPs worldwide in conjunction with high-speed broadband fiber optics internet; the pppoe user space driver is part of Debian's official free repository and it can be used to connect directly to the internet without a router; needles to say it has several use cases. For example, if one's router breaks down, it can function as a temporary fallback. But it can also be used as a permanent solution. Windows has this functionality out-of-the-box. Some GNU/Linux distributions have it by default as well.
cdrtools (it is the only backend for K3b that functions properly; since Neptune is more of a multimedia workstation distribution, I believe that it needs to have K3b functioning properly; I used to use it in Buster. In Bullseye, Debian made wodim a hard dependecy of K3b. Building and packaging K3b as a Neptune-specific package is most likely the best approach. https://cdrtools.org/
smaragd (it's somewhat similar to aurorae but better; If I recall correctly, the following prerequisites are necessary in order to build it from source: git build-essential cmake qtbase5-dev libkf5config-dev libkf5coreaddons-dev libkf5i18n-dev libkf5widgetsaddons-dev libkdecorations2-dev libglib2.0-dev libcairo2-dev extra-cmake-modules gettext. And the following build script should work:
git clone git://anongit.kde.org/smaragd.git
cd smaragd
git checkout kdecoration2
mkdir build && cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr ..
make && sudo make install
Note: instead of make install, you can probably capture it into a cleanly removable .deb package with https://packages.debian.org/bookworm/checkinstall
Checkinstall is obviously not the best method to build a .deb package, especially if you want to make it a Neptune-specific .deb package.
Open Snitch (it's the GNU/Linux analogue of Little Snitch in MacOS; It's been PureOS's long-standing desire to have it; AFAIK they still don't have it but MX have it as a .deb package in they MX-specific repo. I think it's worth investigating.
Abrowser (this one is really worth looking into; it's a Firefox derivative. https://archive.trisquel.info/trisquel/pool/main/f/firefox/; you can use dpkg -i or APT pinning to check it in Neptune.
Thanks for having had the patience of reading through.