I think this is by design; applications are supposed to build
against the systemd headers and then, if they only use functions
also exposed by libelogind0 they can also run with that.

As Thorsten has already suggested, this is by design. Debian packages are only
built against libsystemd-dev. The libelogind0/libsystemd0 compatibility is a
*runtime* option, not compile-time. We don't even know (and can't test) if all
of the source packages depending on libsystemd-dev will compile against
libelogind-dev.

> Please add Provides: libsystemd-dev to control.

This would be both unwise and counter-productive. Having libelogind0 provide
libsystemd0 was a very controversial move and getting it accepted into Bullseye
a hard won victory. I am very reluctant to do anything that might jeopardise
that.

If you have an libelogind0 system and need to compile against libsystemd-dev,
please use one of the various build chroots or containers. This requirement is
already documented in libelogind0's README.Debian.

Connected to this? https://github.com/elogind/elogind/issues/170

# apt update
apt source gnome-settings-daemon

You shouldn't have to do that at all, the libelogind0 package has Provides: libsystemd0.

SOLVED:  sound works now, after reading RELEASE NOTES, and editing the obscure, incomprehensibly named file "00-disable-autospawn.conf", to REMOVE (unintuitive--why would anyone have to comment out a line of code to enable something to work, normal software engineering works in just the opposite fashion, edit a file to add something desired--here we are removing a constraint which prevents what we NORMALLY expect, from happening.) Devuan demands that every user insert a pound sign, " # " in a line of code in a configuration file, to be able to hear sound as expected. 
That's just too much 1960's architecture for my taste.  I am seeing cold rooms with big tape drives, and heavy security to access the wonderful IBM hardware.  NOT for me.

(Editing this silly file is certainly not required to hear music, in running Cinnamon on any other distro, that I have used, e.g. Mint 17.1, Debian Squeeze.)

Pulseaudio
- If you have no sound, make sure the following line in
   /etc/pulse/client.conf.d/00-disable-autospawn.conf is commented as
   shown here:
   #autospawn=no

In other words, the much vaunted, highly touted "RELEASE NOTES", illustrate how that line in the file must look, AFTER editing, by each user of Devuan.   BEFORE editing, that line of text reads like this:
   autospawn=no

To listen to music, with Devuan, but not other Cinnamon versions, one must insert a pound sign into a line of text, to disable that text.

I am very keen to learn which page of Donald Knuth's "The Art of Computer Programming, volume I", corresponds to this notion, demanding that users comment out a line of code in order for a particular function to work as one normally would anticipate, upon successfully completing an installation of Devuan.

Why would several forum participants request/demand "relevant troubleshooting information", to solve this problem?

What is the difference between ADDING a pound sign in front of a line of code not required, vs, changing the code to read:
   autospawn=yes

?
What is it about "system D" that enables that collection of code to permit the user to hear music at once, upon completing the installation, vs whatever it is that Devuan uses to replace "system D", i.e. why should "system D" enable sound, but not whatever it is that Devuan is using?

caieng

The latest version of the firefox-esr package in beowulf is also 78.4