The LED strip appears to be a simple 4 wire RGB 24V strip, they are widely available, but the control is via the LINBus which connects the control panel to a VW module dedicated to the LED function that in turn supplies the 3 x RGB signals. That module is only present when you have the factory ambients but If you can get hold of it then its probably relatively easy to replicate the factory setup. The 24V is provided by a Victron 12:24 off the shelf component. SSP599 page 33 describes the setup more clearly, see attached, as well as how to get into the factory menu of the control panel.