Now, my experience was only me trying to use buildiso to make an iso file with LXQt as the DE and runit as the init daemon, so i don't know if this applies to other desktop environments.
But, when using buildiso, it would always try to install sddm-theme-artix, which is not present in the database, most likely in place of artix-sddm-theme.
The cause of this was profile.yaml, found in /usr/share/artools/iso-profiles/lxqt/profile.yaml, which in the section where it needs to download packages for the installation, it has (a possibly outdated) sddm-theme-artix.
Now, my experience was only me trying to use buildiso to make an iso file with LXQt as the DE and runit as the init daemon, so i don't know if this applies to other desktop environments.
But, when using buildiso, it would always try to install sddm-theme-artix, which is not present in the database, most likely in place of artix-sddm-theme.
The cause of this was profile.yaml, found in /usr/share/artools/iso-profiles/lxqt/profile.yaml, which in the section where it needs to download packages for the installation, it has (a possibly outdated) sddm-theme-artix.