Pipewire settings ignored at startup

I found out that 5.1 surround sound isn’t enabled, although the sound profile is set to “Analog 5.1. Output”. Therefore I have to add

stream.properties = {
channelmix.mix-lfe = true
channelmix.upmix = true
channelmix.lfe-cutoff = 120

to /usr/share/pipewire/pipewire-pulse.conf. 5.1 is enabled after restarting Pipewire using systemctl --user restart pipewire pipewire-pulse pipewire-media-session. The problem is that I have to call this after every reboot, so I added this line to my startup programs. But this is not really sufficient. I wonder why these settings are not effective after boot. Is there a way to make the settings permanently without restarting Pipewire?

# Copy and edit this file in /etc/pipewire for system-wide changes
# or in ~/.config/pipewire for local changes.
# It is also possible to place a file with an updated section in
# /etc/pipewire/pipewire-pulse.conf.d/ for system-wide changes or in
# ~/.config/pipewire/pipewire-pulse.conf.d/ for local changes.

Changes you make under /usr/share/pipewire/ are overwritten when PipeWire receives an update.
Have you tried making device-specific changes?

No, I didn’t. Of course 5.1 should only be applied when using speakers, and not to headphones. So my approach is probably wrong. Where can I change the settings according to speakers?

By copying and modifying alsa-monitor.conf, if you use pipewire-media-session (seems to be the default in Manjaro).
Things go a bit differently if wireplumber media session manager is used instead.

Hm, strange. I removed my changes in pipewire-pulse.conf, and after restarting Pipewire I have 5.1 sound. So there are no additional settings necessary, but Pipewire has to be restarted. The question remains, why Pipewire does not keep the configured profile, and does this only after restarting Pipewire.

I cannot say, since, for me, PipeWire configuration changes have always stuck after a reboot or restarting the service.