For me most things I do on a screen are fairly mentally stimulating (like video games), and even the ones that aren't (like watching a movie) inhibit the feeling of sleepiness I get when I abstain. So, it's better for falling asleep quickly.

I believe it's much to do with blue light emitted by screens:

https://pmc.ncbi.nlm.nih.gov/articles/PMC9424753/

I had heard that that wasn't as much of an effect as some people think - https://www.bbc.com/future/article/20260407-the-blue-light-f...

or rather, that its less about blue light specifically, and more about activity and bright light in general - the times where we are active are shifted later, and a profound lack of exposure to bright light during the day is the issue. Even with the massive amount of screen time the average person gets in a day, that much light adds up to less than a single minute of the equivalent of sunlight.

Probably the best thing you can do is go outside as soon as you can from when you wake up, and stay outside as long as you can. Failing that, get some good BRIGHT sunlight lamps. way brighter than you think could possibly be necassary