A few days ago, out of boredom, I read the FP4 Repair price list which actually mentions an LED as part of the core module:
PCBA: Motherboard and daughterboard housing SoC Qualcomm Snapdragon 750G (SM7225), SIM card slot, SD card slot, microphones 1, 2 and 3, ambient light sensor, proximity sensor, LED, Fingerprint sensor, volume buttons, power button, midframe.
Thus, I reached out to fairphone support and asked them wheter this mention is true or false.
And actually, it’s true. the core module has a built-in LED:
Dear XYZ,
The core module houses an LED inside. But it is not in any way connected to the user experience. It is simply a part of the build of the core module and the motherboard which it contains.
If you have any further questions please let me know. I am happy to help!
Best regards
If the statement of the support is confirmed, there might be still a chance for other OSes to include this functionality - assuming, of course, that the LED is in the right position 