I also encountered the jack2 pipewire-jack conflict issue. The method I used to resolve this conflict is by reinstalling pipewire-jack. It automatically removes jack2 so that the update can continue.
This seems to be resolved:
Name : pipewire-jack
Version : 1:0.3.45-1
Description : Low-latency audio/video router and processor - JACK support
URL : https://pipewire.org
Licenses : MIT GPL2
Repository : extra
Installed Size : 694.6 kB
Groups : --
Depends On : sh pipewire-session-manager libpipewire-0.3.so=0-64
Optional Dependencies : jack-example-tools: for official JACK example-clients and tools
Required By : blender ffmpeg fluidsynth gst-plugins-good portaudio qemu recordmydesktop
Optional For : alsa-plugins manjaro-pipewire mlt mpg123 pipewire sdl2 vlc
Provides : jack libjack.so=0-64 libjackserver.so=0-64 libjacknet.so=0-64
Replaces : --
Conflicts With : jack jack2
Packager : David Runge <dvzrv@archlinux.org>
Build Date : Thu Feb 3 18:26:02 2022
Install Date : Sat Feb 5 11:37:36 2022
Install Reason : Installed as a dependency for another package
Validated By : Signature
Backup files : --