I have successfully installed OpenWrt on a Linksys E8450 (JP) by following this guide
I followed this guide to set times where OpenWrt is supposed to drop internet connectivity: https://openwrt.org/docs/guide-user/firewall/fw3_configurations/fw3_parent_controls#time_restriction_of_internet_access
I moved the resulting rule all the way to the top. The time of the Linksys is correct (UTC unchecked).
But the behaviour is not as expected (or described in that article). When the times are passed Internet connectivity is still there. This is for both devices that are already connected at the time and for devices that connect after the time has passed.
The rule is listed in the GUI, but not in /etc/config/firewall, even after submitting fw3 reload.
Any pointers would be appreciated.