Antony Stone wrote:
> My definition of skipping releases would be:
>

>     Ascii (skip Beowulf) -> Chimaera

>

>     Stretch (skip Buster) -> Bullseye

>

>     Stretch (skip Buster or Beowulf) -> Chimaera

Agreed. Those would be skipping releases. Not supported.

> I'm not asking about any of those.

I almost trimmed all of the above out of my response here. But left
it because it is good to have confirmation and clarity and the above
are good concrete examples.

> I'm asking about going from one version of Debian to the next version of
> Devuan.

>>> - upgraded and migrated from the previous Debian release (eg: Stretch -> Beowulf)
>>> Is that last option still valid for eg: Buster -> Chimaera?

First, I am not an authoritative answerer, caution, this is just me, but...

I think what you are asking is okay to do and you can be successful
doing it. I have done it several times with success. But this might
be because of what I have or do not have installed or because I have
extensively cleaned my system before the upgrade. With any upgrade
the best success is when it has had the best preparation.

    https://www.proulx.com/~bob/doc/bobs-guide-to-upgrading-debian/bobs-guide-to-upgrading-debian.html

I think what you want to do will work but it is not the documented
procedure. The documented procedure is to go from Debian 10 Buster to
Debian 11 Bullseye and then from Bullseye to Chimaera. That's well
documented within each OS. So you are somewhat skipping one of the
connecting points. But you are NOT skipping an OS release in the
classic way that is definitely not supported. You will be seeing all
of the transition points along the way. Transitions dealing with
Perl, Python, and so on of all of the library transions.

The important thing is to be aware of the manual steps needed to step
from systemd as init to a supported init in Devuan. The process is
well documented for going from Bullseye to Chimaera here.

    https://www.devuan.org/os/documentation/install-guides/chimaera/bullseye-to-chimaera

If you decide to avoid the Debian 10 Buster to Debian 11 Bullseye
upgrade and go directly to Devuan 4 Chimaera then you are stepping
outside of the well traveled path. Depending upon the exact
collection of packages you have installed on your system there might
be some snag that would cause problems. If you feel confident of your
abilities to self-rescue things in the case of problems then I don't
see any major reason it would not work for you.

But why tempt fate? What's the actual savings of avoiding the
traveled path? Chimaera is an overlay on Bullseye. Therefore
upgrading from Debian 10 Buster to 11 Bullseye is actually on the path
to Chimaera. And then the upgrade form Bullseye to Devuan 4 Chimaera
is a much smaller upgrade than from Devuan 3 Beowulf. Most packages
are the exact same packages. Only a few are different.

If I were upgrading a 100 servers in a datacenter then I would test
upgrade a handful to verify the process and then do all of them and it
would save quite a bit of time. But if I were just upgrading my own
desktop and just wanted to get done then I would just go ahead and do
the documented path. It would save time in the long run to stay on
the path. Slow is fast and fast is slow.

On the other hand if it was me and I wanted to test if this were
working then I would snapshot a VM for perfect safety and then try it
and see what issues occurred. Do it on something that if it failed
that it would not be a problem.

Good Luck!
Bob