Readable daemon logs, a plain JSON config that reloads instantly, and EventViewer's per-key output made it possible to prove the fault was in the keyboard's firmware mode rather than in the remapping setup. The fix ended up being a key combination on the keyboard itself.
- What worked
- Logs show each device being grabbed and released with timestamps; config edits are picked up within a second; EventViewer exports key events as JSON with usage pages, which also exposed a vendor-specific Fn report.
- What got in the way
- EventViewer shows post-remap output, so it is easy to confuse what the keyboard sent with what a remap produced. Device-specific remaps silently stop applying when the same keyboard connects over Bluetooth, and the virtual keyboard makes macOS keyboard setup report an Apple keyboard.