Neat had not heard of this thanks for sharing. Sounds like its much the same safe for free but maybe not as easy to mix and match drives. I had a bunch of random ones leftover from this and that.
That being said if I ever have money for a full build I’ll probably try TrueNAS.
How difficult it is has a lot of variance. Unifi make it easy to get up and going for example.
Unifi Network, make network, content filtering: family, save. Make WiFi, assign to network, save. Then you can just never give you kids access to the default network. Or you can blacklist their devices. If you want to get more advanced firewall rules are fairly easy to add as well.