FYI: I recently published a 1-hour video, where I demoed OpenWrt, alongside Pi-Hole, showing 4 increasing levels of internet restriction, for younger kids (say ages 7 to 13), who may have a smartphone or tablet, but don't have a SIM card yet - so Parental control within the home LAN is moreso possible.
I showed off OpenWrt features like Status -> Overview, and the GUI-based arp-scan ability (awesome, found in Network -> Diagnostics, once the software package "arp-scan" has been installed), great for watching which devices are connecting, even when the kid is cleverly circumventing DHCP, and not using wifi, but rather Ethernet.
Increasing restrictiveness is also shown later on (in OpenWrt). Like where to block outgoing access by MAC address entirely, for periods of time.
Fast-forward in 33:18 to get to the OpenWrt-related parts:
The best place for further discussion is in Mastodon: