Am Sonntag, 14. November 2021 schrieb Haines Brown:
> Given the absence of a backport for nano, my aim is to construct
> a .deb for the testing version of nano (nano-9.5). This is what I
> did:
>
> In apt sources.list IO added the lines
>

>     deb http://deb.devuan.org/merged chimaera-backports main contrib
> non-free deb-src http://deb.devuan.org/merged chimaera-backports main
> contrib non-free

Above you showed that you added the lines for source repository
of "chimaera-backports"… Why not "testing" if that is where you want
to build from?

> I expected # aptitude search nano would now return a nano package
> with the .bpo extendion. It did not. Whe not?

You already said that there is no backport version of nano.

> Next I tried to satisfy dependencies:
>
> # apt-get build-dep -t testing nano
> but this returns:
>

>   E: The value 'testing' is invalid for APT::Default-Release as such
>     a release is not available in the sources

        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I guess that you don't have entries for release testing in your
sources.list…

If you want to compile a testing version of nano then you need the
source repository for the testing release, not the "chimaera-backports"
one, I think.

HTH

Kind regards,
Stefan