I was able to build and run it without much issue, but it likely didn't complain since I built it on my own machine. It's quite common to encounter these kinds of issues for indie software (un-notarized) on macOS, but there are quite a few ways around it.
Although macOS will complain about not being able to run the un-notarized executables, it's still possible through a variety of means which can be done by the end-user, though at times they can be a bit inconvenient.
If you ad-hoc sign the application (doesn't require a developer account to my knowledge, just enable add the "Disable Library Validation" entitlement beforehand), I think it would just require right-clicking or control-clicking to open instead of double-clicking to open.
Take a look here:
- https://docs.godotengine.org/en/stable/tutorials/export/running_on_macos.html#ap...
- https://support.apple.com/guide/mac-help/mh40616/
The only issue after building was that the built-in fullscreen didn't work and just added a black background with the game in the top right, but after disabling it you can use the native window controls to fullscreen it without issue.