[Resolved] Missing audio with MPV + Wayland

So I know my setup is really niche, but here goes nothing

• I am using Arch Pi on Pi 4
• Installed cage as a lightweight Wayland compositor
• Installed mpv + wireplumber + pipewire

I am not quite sure how to use cage to launch a simple "Wayland session (if it even makes sense)", so that I can send MPV to that display. So I tried cage -s alacritty :1, and it does launch alacritty with it detecting that it is on wayland.

But when I do DISPLAY=:1 mpv ...., the video runs, but there's no audio. Also there's no errors shown on mpv either.

The other thing of note is that I tried cage -s Xwayland :1 and the audio+video works perfectly.

So in all:

1. How do I launch cage to spawn a simple Wayland session? Is this even possible?
2. How do I solve the audio issue on Wayland?

EDIT: Thanks all for the help. After some investigation, I found out the pipewire somehow is not ran on startup of alacritty, but it did for Xwayland. I noticed that the first play of the video would be audio-less on alacritty, and subsequent ones are fine. It seems like the first run causes pipewire to be started and thus I wrongfully assumed that the daemon was running.

Still strange nonetheless...