On my recently installed OMV6 System I get following Error Message when I try to install openmediavault-kvm.
Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C.UTF-8; export LANGUAGE=; export DEBIAN_FRONTEND=noninteractive; apt-get --yes --allow-downgrades --allow-change-held-packages --fix-missing --allow-unauthenticated --reinstall install openmediavault-kvm 2>&1' with exit code '100': Reading package lists...
Building dependency tree...
Reading state information...
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
openmediavault-kvm : Depends: qemu-system-ppc but it is not installable
E: Unable to correct problems, you have held broken packages.
OMV\ExecException: Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C.UTF-8; export LANGUAGE=; export DEBIAN_FRONTEND=noninteractive; apt-get --yes --allow-downgrades --allow-change-held-packages --fix-missing --allow-unauthenticated --reinstall install openmediavault-kvm 2>&1' with exit code '100': Reading package lists...
Building dependency tree...
Reading state information...
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
openmediavault-kvm : Depends: qemu-system-ppc but it is not installable
E: Unable to correct problems, you have held broken packages. in /usr/share/openmediavault/engined/rpc/pluginmgmt.inc:247
Stack trace:
#0 /usr/share/php/openmediavault/rpc/serviceabstract.inc(619): Engined\Rpc\PluginMgmt->Engined\Rpc\{closure}('/tmp/bgstatusl5...', '/tmp/bgoutputrK...')
#1 /usr/share/openmediavault/engined/rpc/pluginmgmt.inc(251): OMV\Rpc\ServiceAbstract->execBgProc(Object(Closure))
#2 [internal function]: Engined\Rpc\PluginMgmt->install(Array, Array)
#3 /usr/share/php/openmediavault/rpc/serviceabstract.inc(123): call_user_func_array(Array, Array)
#4 /usr/share/php/openmediavault/rpc/rpc.inc(86): OMV\Rpc\ServiceAbstract->callMethod('install', Array, Array)
#5 /usr/sbin/omv-engined(537): OMV\Rpc\Rpc::call('Plugin', 'install', Array, Array, 1)
#6 {main}A quick search on the forum revealed several threads, where ryecoaaron advised people to fix their (in some cases previously messed up) systems by enabling backports. And indeed that fixed the issue for all of them. The thing is, my System is in a nearly virgin state. Yesterday installed on a new ssd from omv6 iso, just omv-extras, openmediavault-nut and openmediavault-compose added, no users nor data drives yet, no weird experiments like nvidia graphics drivers ...
And I'm pretty sure I had openmediavault-kvm installed on my previous OMV6 installation on the same machine without having backports activated. 
ryecoaaron Are enabled backports a pre requirement for openmediavault-kvm now? If so, this should be mentioned somewhere in the documentation.
I have to say that I'm not so at all comfortable with enabling backports system-wide. So I didn't try it yet. Feels a bit like a solution that could break anytime (kvm or other system components). 
I remember some sleepless nights years ago recovering a system screwed up by me having lighthearted enabled backports before. 
edit: If (some) backported packages are needed for installing kvm now, is there a way to automate that install process so that it doesn't require enabling backports system-wide?
edit2: I'd still prefer a solution without backports at all, but if this is not possible ...
