I had this bug with the current version that is in the main package universe of Ubuntu (2.2.3 I think), as well as Audacity 2.3.2 (installed from ppa:ubuntuhandbook1/audacity, after complete purge). I never had this bug in the last years until approximately one month ago.
I cannot open any FLAC file. My default view is the spectrogram view. The spectrogram is generated for all files that are dragged onto Audacity one by one but at the point where processing would end, I get this error message:
File error - Audacity failed to read from a file in /media/…
You should be able to reproduce it with this file:
Happens when the file is stored locally or externally.
I use the latest Ubuntu (19.04).