On my family's iPhones, we have a Shortcut (automation) that kicks in every evening at 9 pm:

1. Turn Mobile Data Off

2. Turn Bluetooth Off

3. Turn WiFi Off

4. Turn AppleTV off (this one is fun because it can cut off a show mid-sentence)

5. Set brightness to 10%.

Then, a reverse of the above at 6am the following day.

Normal phone signal is still enabled for any emergency calls, but most apps become useless without the internet.