I tired to install musescore with synaptic. It fails because of some dependencies:
1. libportaudio2 (is also in synaptic)
2. qtbase-abi-5-5-1 (is not in synaptic)
3. musescore-common (is also in synaptic)

I think the problem is with qtbase-abi-5-5-1
On Google I can find that this is a virtual package and it should be covered by the package libqt5core5a. But this package is allready installed.

How can I solve this problem?

I use neon user edition

It's are the same reasons as here. Unluckily there is no solution at the moment.

at he moment I run musescore from an appimage.