Hi,
I had the same dependency problem and I did the following:
I ran
sudo pacman -Sdd pipewire-jack
This reinstalled pipewire-jack and removed jack2 but left lib32-jack2. So I forcefully removed only lib32-jack2 with
sudo pacman -Rdd lib32-jack2
Then I proceeded with the update as usual and it asked me for a provider for lib32-jack.so. I chose pipewire and was able to update successfully.
This way you don’t have to remove other packages like portaudio and fluidsynth which depend on lib32-jack2 and jack2.
Note: The first -d skips version checks and the second -d skips dependency checks.