apt-get download $(dpkg -I rescuezilla_2.4.2-1_all.deb)
Thanks a lot! While it wasn't as simple as that, it did indeed point me onto the right direction. This command did the trick for me:
apt download $(dpkg -I rescuezilla_2.4.2-1_all.deb | grep -oP '(?<=Depends: ).*' | tr -d ',')
The grep goes there to list only what comes after "Depends:". The -oP enables the python command to remove the string matching itself, so it leaves the whole list after the match... otherwise it also tries to download a package named "Depends:". And the tr -d ',' is to remove the commas separating each package, otherwise it fails to find them.
Thanks! How does this work with OS permissions? As it's rescuezilla and veracrypt I'm trying to use, both need access to the system partitions in order to be able to mount/read/copy to them. Flatpak can be a bit limited regarding permissions...Moreso on a live iso I guess.