This seems to suggest that LED’s can produce pure DC light, with no flashing:
https://www.sunlitest.com/faq/do-led-lights-run-on-ac-or-dc-current/
“LEDs are super fast. If you drive them with DC, they will not flicker. But, LEDs use very low voltage (around 1 volt) and converting 12 or 120 volts to a small DC using resistors or transistor in old-fashioned “linear” regulation wastes most of the power. So, folks usually pulse width modulate (PWM) LEDs. This turns them on and off at a very fast rate. It wastes very little power and allows you to vary the brightness by changing the % of the time it is on. If the on/off frequency is high enough, you can't see any flicker. One issue is that if you move your head quickly, the LED will look like a dotted line. Modern car tail lights have this problem.”