abc-import plugin does not work on ubuntu 18.04

Try running it in the Plugin Editor, this may reveal where it fails

In general, this is due to some missing librairies. Try to run MuseScore on the command line and check the output.
If you really need the feature, you can go directly to https://abc2xml.appspot.com/ which is the webservice called by the plugin.

I had a similar problem on UbuntuStudio 18.04 ; I ran the plugin from the plugin editor, and it showed that a couple of qml-related libraries /modules were missing, most notably folderlistmodel and the Qt 5 settings QML module.
I installed them manually, restarted Musescore and it solved the problem.

I had this problem and found this solution:

Running the abc-import plugin in Plugin Creator produced

Running...
creating component failed
line 47: Type FileDialog unavailable
line 47: module "Qt.labs.folderlistmodel" is not installed
line 48: module "Qt.labs.settings" is not installed
line 47: module "Qt.labs.folderlistmodel" is not installed
line 48: module "Qt.labs.settings" is not installed

SOLUTION

Use Synaptic to load these packages

qml-module-qt-labs-folderlist
qml-module-qt-labs-settings

Start MuseScore and Select Plugins/Plugin Manager and Check abc-import and click OK

Select Plugins and ABC Import

SUCCESS