CHIRP

CHIRP is actually not expected to work on anything older than Big Sur. I'm shocked it works at all on anything as old as you're indicating here. Were it trivial to fix, I might try, but I believe this is just a fundamental lack of support in libraries we rely on (wx) that need a newer version of the OS. On my system here, 'en' is not a valid locale name from the base OS, yet that's what your system is reporting. I'm sure that has to do with changes that have been made since 10.13.

So, if it works enough to use by setting the language manually, consider yourself lucky, but it's not "supposed to work" on something that old. I will soon have to move the support envelope even later than Big Sur as Apple stops allowing me to notarize the build from such an old and unsupported system.