I regularly work with musescore.
Unfortunately, it is impossible to download this software under KDEneon

No wonder, it is not an application that is part of the standard distribution packages, and it is not maintained by us.

Did you check the musescore webpage? In the download section you should be able to download it using the Ubuntu community package. Don't forget to check the dependencies and read the respective instructions about this package.

FWIW: it is impossible to provide download packages for all software available for Linux, there are literally thousands of projects out there. Also, KDEneon is not per se a distribution, but a KDE showcase, therefore the offer is limited to KDE project applications and their dependencies.

musescore may not be provided by Neon, but it is in the Ubuntu (universe) repositories, so presumably one should be able to download it in Neon (or is Neon so divergent that you can't guarantee that users can't download and/or use any package in the Ubuntu repos?).

What messages do you see when you try to download musescore?

MuseScore contributer here. Even if musescore is not provided by Neon, it should still be possible to download the AppImage:

https://musescore.org/en/download#AppImage

Then you make that file executable and you should be able to run it. (The AppImage contains all necessary libraries bundled with it.)

You can also install the AppImage: https://musescore.org/en/handbook/insta ... ge-install