Hi, long time no see. I am reading the same problem here (sorry, it is in Dutch):
https://www.macfreak.nl/hardware-macintosh/cinema-display-24-zwart-scherm-nog-wel-communicatie-via-display-port/msg563666/#msg563666
Seems to me many of those 24” Apple Cinema Displays have damaged backlight inverters.
Looks like a generic issue.
Any chance we get that inverter board as a spare on iFixit.eu?