LED light. AC Voltage input from transformer. An LED requires DC Voltage to work. Does this work with an AV Voltage input?

Generally you would be correct most LED applications require an LED driver to convert AC to DC as DC voltage is generally significantly lower than AC current. Most products in todays market will come with a built in LED driver to avoid confusion for customers wondering what driver could be compatible. This doorbell does not require a driver as your doorbell transformer should be decreasing your voltage to anywhere from 9 to 24 volts to your chime and push button. This would mean that the AC current is now low enough voltage for an LED, and not all LEDs require DC voltage to work. I hope this helps, all the best!