Well, now that you have edited it, it reads "daedalus" although when first posted it read "deadalus"

Actually, I think that was me. When there are obvious misspellings of Devuan releases, I will correct them to prevent further confusion.

Sometimes you get errors if you hit a mirror just when it's updating, and in those cases, it works again after a few minutes.

And sometimes a mirror is down. If it turns out that your sources.list is correct and you still have problems, you could select a specific mirror from this list: http://pkgmaster.devuan.org/mirror_list.txt
You can check the status of mirrors on this page: https://sledjhamr.org/apt-panopticon/re … t-web.html

The text "It cannot be updated from such a repository in a secure way and is therefore disabled by default." also differs from the standard wording.

Are you translating this text? Don't do that. Instead prefix the command with LANGUAGE=en to have Apt output in the specified language (English), and then provide the exact verbatim command and output.

If you haven't yet got a terminal that allows you to copy text, you can do, e.g:
LANGUAGE=en apt-get update |& tee ~/output_of_apt_update.txt

-

Anyway, it looks like there might be an issue with Devuan here - not for non-free, but for non-free-firmware:
curl -isS http://deb.devuan.org/merged/dists/daedalus/Release | grep Release

There are no "Release" files under "non-free-firmware" directories, despite every other section having them...

Edit: Having checked the repository format specification, the "dists/$DIST/$COMP/binary-$ARCH/Release" files are legacy/no longer used (since ~2017), so this is a red herring.

I was attempting to both be light-hearted in my response, and also warning other folks not to blindly copy your [ code ]'ed config since it contained a spelling mistake. Also, I personally only ever 'code' actual results without editing them so that others can trust that what I code is actually what I got as a result.

You need to address your remarks on the absence of non-free to fsmithred, since he states that yes, that does work whereas security & updates will not. I have no personal experience to be able to comment.

@brday:
If your code was copied from the terminal then you likely have a reason (speling), otherwise non-free & contrib are not available for deadalus, though they may be for daedalus.

I said that the repository this does work although it is insufficient:

http://deb.devuan.org/merged daedalus          main

But the non-free repository does not work, let's be clear.

deb http://deb.devuan.org/merged daedalus-security main contrib non-free

The Devuan package information is here, and the sole Default configuration shown for daedalus is as follows on that page:

@brday:
If your code was copied from the terminal then you likely have a reason (speling), otherwise non-free & contrib are not available for deadalus, though they may be for daedalus.

To add the non-free repository in the daedalus test system, how do I proceed?

Edit:
In this way I tried to add, but it gave me error:

En /sources.list

deb http://deb.devuan.org/merged daedalus main non-free contrib non-free-firmware

Typographical correction in the manual copy of the terminal output.

# apt-get update

E: The <<http://deb.devuan.org/merged daedalus Release>> file does not have a Publication file.

N:  It cannot be updated from such a repository in a secure way and is therefore disabled by default.

#

Now the default repositories are commented out like this:

# deb http://deb.devuan.org/merged daedalus-security main contrib non-free
# deb-src http://deb.devuan.org/merged daedalus-security main contrib non-free

The only repositories that work on the daedalus  test system are these, but it is insufficient!

deb http://deb.devuan.org/merged daedalus main
deb-src http://deb.devuan.org/merged daedalus main