How to make rgb LED strip digitally addressable
Put a microcontroller on each strip.  That does the PWM locally for each color of that strip.  You don't want to run PWM lines a long distance anyway.  The signals will be messy at the ends of the wires, and they would emit a lot of RF interference.

Use a micro with CAN built in.  Connect all the strips to a single CAN bus, with a separate master that tells each of the strips what to do at a high level.

It would be convenient to use the same cable for CAN and power.  In that case, you might want to bus around something like 24 V.  That way each strip can make its own 12 V.  With 24 V, there will be less voltage drop along the cable, and with individual buck switchers on each strip, the bus voltage can be anything over a reasonably wide range.  It should be easily possible to tolerate anywhere from maybe 14 V to up to 30 V in at each strip.