Ubuntu Playback (ALSA Workaround)

I've been trying to get playback working on my Ubuntu 22.04 LTS install but had a bit of trouble - in case anyone has had a similar experience I thought it would be helpful to post something here.

In short, Musescore 4 (the appimage) seems to require a jack session running in order to connect to a playback device on my system. Pressing the play button otherwise would not start playback, even though exporting audio works just fine (and sounds very good with the new sample library!).

Since you can no longer choose the audio server in the I/O settings (like PulseAudio, ALSA, Jack, Pipewire), I made the initial assumption that it was an ALSA issue (and the audio settings in Gnome showed Musescore 4 as an ALSA plugin), but noticed that running the appimage from the terminal showed two libraries running - /lib/x86_64-linux-gnu/libjack.so.0 and /lib/x86_64-linux-gnu/libnss3.so

Since ALSA isn't listed in these startup messages I assume that it's not actually using ALSA to connect to my sound device.
I tried using pipewire (with the application qpwgraph), where Musescore would show as an ALSA plugin but connecting it to an output device or another application would not solve the playback issue. Closing all other applications that use PulseAudio (mail, web browser) also didn't solve the issue as it might do with a program trying to take control of the same ALSA device. Some previous support posts on the forum here also had ALSA issues, but the were always a problem with the user's ALSA configuration or .asoundrc file. I should mention that I use ALSA all the time with Bitwig, Pure Data and Ardour, so I was pretty sure it wasn't the issue.

Running QjackCtl to start a JACK session and then opening Musescore worked a treat though! The transport proceeds to playback and sends audio through a PulseAudio JACK Sink to the system outputs.

Note that without a jack session running, quitting Musescore still leaves the ALSA plugin running in the System Monitor and is still visible in the Audio Settings in Gnome (and every instance will continue to stack up until my computer is restarted).

I hope this helps someone!

My installation for reference:
OS: Ubuntu 22.04.1 LTS
Arch.: x86_64, MuseScore version (64-bit): 4.0.0-223472159
revision: 5485621
Audio card is the built-in Intel PCH
I use the Ubuntu Studio installer as well for the low latency kernel and repos

Screenshots of the Jack Graph and Audio Settings are attached for reference.