it seems to have gone kaupt.
FR24 has a day/night display when playing back a recorded prior flight, awkward to use. Could not get flightaware or flightstats to that, their day / night views appeared static.
Could not find a direct equivalent to sunflight.net

Generally with a little thinking you can figure out -- east-west flights(sun mostly on the south depending on the latitude) are the north-south are harder. In between varies