How can I downmix stereo audio output to mono in PipeWire (on 22.10)?

I need a way to set mono audio output on my system.
I had used this solution before: Can I downmix stereo audio to mono?

pacmd load-module module-remap-sink sink_name=mono master=NAME_OF_AUDIO_SINK \
 channels=2 channel_map=mono,mono

However, it stopped working when I upgraded to Kubuntu 22.10, presumably because it now uses PipeWire instead of PulseAudio. When I do pacmd list-sinks I get:
No PulseAudio daemon running, or not running as session daemon.

How can I do the same (downmix stereo audio output to mono) on PipeWire?

I found here a solution to a similar problem, but if I understand correctly that's for getting mono input. I want mono output.
Even better if I can easily switch it to mono/stereo using GUI, or set it to mono only when my stupid earphones are connected.

PS: They should really implement Mono Sound as a profile/configuration on System Settings > Audio, but oh well...

Maybe you could use qpwgraph and link both L and R channels in a manner similar to this:

Profiles can be saved, but for that I redirect you to the docs. Here is a bit about saving and loading profiles with pipewire on ArchWiki: https://wiki.archlinux.org/title/PipeWire#PipeWire_patch_sets_for_command_line

• Another solution without the need to install another program would be creating a mono output configuration file for PipeWire.

• For example the following configuration can be done per user session:

  • Create a mono-playback.conf in ~/.config/pipewire/pipewire.conf.d with the following:

    context.modules = [
        { name = libpipewire-module-loopback
            args = {
                node.description = "Mono Playback Device"
                capture.props = {
                    node.name      = "mono_output"
                    media.class    = "Audio/Sink"
                    audio.position = [ MONO ]
                }
                playback.props = {
                    node.name      = "playback.mono_output"
                    audio.position = [ MONO ]
                    node.passive   = true
                }
            }
        }
    ]
    

  • Restart pipewire service:

    systemctl --user restart pipewire{,-pulse}.{service,socket}
    

  • This will create a virtual device (a sink in this case) named Mono Playback Device

  • The device can be selected by GUI from an audio applet or system settings. Example using KDE Plasma audio applet.

• For Further reading to understand the options you can refer to PipeWire Wiki, Virtual Devices section.