In v1.4.0 it was just that the core loaded with -L wouldn’t be selected by default, as I described in this bug report:
Now in v1.5.0, the -L option doesn’t work at all. RetroArch won’t even launch if you try to load a core with -L
Confirmed it’s still broken in today’s Nightly build. Guess I’ll open a bug report on github.
Doe! I was forgetting the --menu prefix … geez, nevermind, it’s working.