I get the following error using Frescobaldi 3.1.2 with LilyPond 2.21.1:
Converting to ...pdf'...warning: g_spawn_sync failed (0): gs: Failed to execute child process “gs” (No such file or directory)
No error when invoking lilypond from the command line No error with version 2.20 macOS 10.15.4 LilyPond 2.21.1 (Macports) LilyPond 2.20.0 (from Marnen) Frescobaldi 3.1.2 installation kind: standalone .app bundle Thomas