Not necessarily, there are many LCD monitors without PWM: https://www.rtings.com/monitor/tests/motion/image-flickerLCD also. The LEDs are with PWM.
And for example neither the SE3 nor the iPad 10 or Air have PWM:

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The iPad Pro does seem to have PWM, though at a very high frequency: https://www.notebookcheck.net/Apple...tablet-now-runs-with-the-M2-SoC.671454.0.html
The iPad mini has PWM at brightness settings below 10%, however using an even higher frequency: https://www.notebookcheck.net/Apple...attractive-small-tablet-with-5G.573625.0.html