I finally managed to install MuseScore, more or less, after a couple of days hung up in 503 errors. Finally I got “installation complete”. But then when I try to run it, I’m getting
error: app/org.musescore.MuseScore/aarch64/master not installed
Help? Thanks a million
Woohoo, I’m in! The app is up and running. I have no idea why – I powerwashed my Chromebook for an unrelated reason, reinstalled Linux, reinstalled flatpak and the repo, and installed MuseScore. I only got the 503 server error once this time before success, and it ran fine. So I guess this topic can be closed!