I cannot find the words to express my gratitude for finding this thread. I started my Gregorio journey in late 2022 on Windows 10 with a full install of TeX Live and using TeXworks as the editor. Then in early 2023 I started using Ubuntu 22.04 as my on-and-off daily driver. With some help from
this thread, I replicated my TeX Live and TeXworks setup as I had it on Windows.
When I upgraded to Ubuntu 23.10 in late 2023, TeXworks would not compile the chant and gave me the same "Unable to find gregorio executable. shell-escape mode may not be activated." error. I uninstalled and reinstalled Tex Live and TeXworks, I upgraded to Ubuntu 24.04, and all to no avail. I threw up my hands and resigned to running Gregorio on Windows 10 (which always worked).
Just in the past month (April 2025) I installed EndeavourOS (Arch-based Linux distro) on an old laptop. I wanted to give Gregorio another try on a "new" machine and, alas, the same error came up from TeXworks. Then Rob Leduc gave me the idea to just run the compiling step through the command line. So logged in to my admin profile and simply running
lualatex --shell-escape low_off.tex
in a terminal in the folder where I have all my files produced the PDF of the Low Sunday Offertory I prepared on TeXworks. I'm far from a computer expert, but my anecdotal experience may lend credence to the theory that some security patch was pushed on Unix / Mac systems that prohibit shell-escape to be run from applications but not from the terminal.