I saved my dpkg --get-selections on my Devuan ASCII (~= Debian Stretch). I've now reinstalled my system cleanly and dist-upgraded to Devuan Beowulf (~= Debian Buster).
Is it safe for me to now dpkg --set-selections? If not, can I filter out the unsafe selections and use the rest?
Yes, it is. All that can go wrong is that you end up attempting to select packages which have been removed; in that situation,
unknown packages will be ignored with a warning.
(See the dpkg manpage.)
You could also end up selecting deprecated packages; however you’ll end up with the appropriate transitional packages. (This could be more troublesome if you were skipping a release.)
Another possibility is that you select conflicting packages (between your selection and the upgraded packages), but the follow-up apt should be able to sort that out, or at least give you enough information for you to sort it out.
Debian, and presumably Devuan, cope fine with upgrades without re-installing, which would avoid your conundrum entirely. My main Debian system is running a Debian install which has been upgraded over the years going back to Debian 2.0!
