What is this black, marking-less, 6-pin surface mount device?
Did an image search for reflective optocoupler.

Found one that looks similar.

It may be a SFH 9245 Osram Opto, SMT Reflective Optical Sensor, Phototransistor Output.

Here is the datasheet.

https://docs.rs-online.com/aa9a/0900766b811e0651.pdf

edit:  google osram reflective photointerrupter