Suggestion based on our parenting results, YMMV:

1. Enforced limits are adversarial.

2. Conversations around how the internet/devices etc are fantastic while fraught with a million pitfalls may seem too much for a 9yo to handle, but you might be surprised if you try.

3. In general, having healthier alternatives and some timely reminders work great. For example: If he is spending hours browsing the lego website, perhaps he'd love to try out a large lego project.

4. Teens and pre-teens right now will inhabit a world that is over-reactive to online stimuli. Being hygienic / responsible about the online world and screen time is an important skill to cultivate.