Thanks @GhostLegion, that helped in the sense that I now know that my key map configuration is not completely off.
Also the blacklist hid-sensor-hub workaround allowed me to get events for Fn+F7..F8:
# acpi_listen
video/brightnessdown BRTDN 00000087 00000000 K
video/brightnessup BRTUP 00000086 00000000 K
Now I’m down to no events triggered for Fn+F9..F12.