OK, I think I have figured out how to read the data now. Timing is key.
The WS2812b LED strips I am using have very specific timing requirements for the data being sent up the data line.
So reading the SP107E output is just a matter of determining what is happening in the period of time to send, as per these timings.
If the reading at 2us is LOW then the data being sent is the RESET code. No need to read the next position at 6us as RESET is all it can be. If the reading is HIGH, then take a reading at the 6us position. If the reading is HIGH then the bit can be set to 1 else it will be 0. We can build the 24bit segment for each LED and then send it to the Slave D1 Minis and use FastLED to show the pattern. Not sure how much latency there will be.
Just need to code this now.