Ciao.
From the compialtion log, the error arising when using the 5.15.2 version is:

2023-06-04T16:08:50.7841280Z ERROR: "error: /Applications/Xcode_12.4.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/strip: can't write output file: /Volumes/MuseScore-3.7b-cacdcc9/mscore.app/Contents/Frameworks/QtWebEngineCore.framework/Versions/5/QtWebEngineCore.strip (No space left on device)\n"
2023-06-04T16:08:50.7842000Z ERROR: ""
2023-06-04T16:08:50.8032710Z ERROR: Could not parse otool output: "/Volumes/MuseScore-3.7b-cacdcc9/mscore.app/Contents/Frameworks/QtWebEngineCore.framework/Versions/5/QtWebEngineCore: is not an object file\n"

during the package step. Indeed, inside the dmg file there is Contents/Frameworks/QtWebEngineCore.framework/Versions/5/QtWebEngineCore but it is empty (0 bytes).

The QtWebEngineCore file exists inside the 5.15.2 archive. I don't know if it is a problem of actual total disk space (I doubt it), or if it tries to create some sort of logical volume and that is not big enough.

To save space, you can try to delete Visual Studio for Mac, that is not used for building MuseScore:
[you maybe need sudo before each of these commands]

rm -rf "/Applications/Visual Studio.app"
rm -rf "/Applications/Visual Studio 2019.app" 

Here you can find all the software installed on the virtual machine: https://github.com/actions/runner-images/blob/main/images/macos/macos-11-Readme.md some of them can be unistalled/deleted to gain free space (if that is what really is needed for the "No space left on device" error).

Try to see if #129 solves the problem. 🤞

Prevent accidential merge ;-)
We still may want to downgrad back to Qt 5.9 eventually though.

See also #127