With my kids, I oversee everything they do (they are under 6). They average 15min daily for two episodes of a kids show.
I'm not saying go to zero. But definitely not over 3 hours and definitely not a dedicated device for them.
The idea is to send a signal that this is not ok. I have no guarantees on effectiveness. What especially gets me going is when the kid eats and looks at some trash like baby shark while it's blasting loud everywhere.
Regarding my kids: high priority, wide/curated choice (not in terms of restriction, but in terms of actively finding things they may like), accompanied learning, and, crucially, starting from a very young age. It's pretty much standard parenting, that is, one gets out what one puts in.
By the time children start to pressure for this type of devices (say, 10/12), they will have learned to enjoy books and more creative activities.
Mobile devices and social media does not get less addictive as you get older, otherwise anybody over about 30 right now would never have any issues with it. Therefore I worry its entirely possible to bring your children up completely avoiding the downfalls of screentime, but then set them up to fall later because they havent developed the guards against it or even havent 'got it out of their system' so to speak.