MS3-RC does not want to quit.
1. Ubuntu restarted.
MuseScore 3 RC started, at the start-center "Schließen" entered (no file loaded).
"ged" started and placed next to MuseScore.
In the MuseScore menu "Hilfe->Über MuseScore" selected; button next to revision pressed.
Clipboard content copied into ged by Ctrl-v:
OS: Ubuntu 18.04.1 LTS, Arch.: x86_64, MuseScore version (64-bit): 3.0.0., revision: 96c1f7b
In the menu "Datei->Beenden" selected; no reaction.
Ubuntu "Systemüberwachung": no significant load on the system.
In the MuseScore wildly pressedon anything; no reaction, menu not active. Press on "red x in the window frame" leads to Ubuntu PopUp "MuseScore does not answer."
"Warten" does not help. Only "Beenden erzwingen" stops the program.
See also my post https://musescore.org/de/node/279538, where kuwitt urged me to report it to the issue tracker. Unfortunately, I have no idea how to fill the requested fields correctly.