While no system is perfect, technology has improved a lot since you were a kid.

For one, like it or not, many phones no longer allow custom ROMs or tampering. But even that aside, network inspection takes way less processing power now so a basic gateway can now handle dynamic block lists, DNS filtering, VPN detection, etc. If properly implemented it could ensure your parent’s use a password with good complexity and require MFA in order to turn it off.

Now, circumvention techniques have improved as well, but cheap cryptography really changes things and it can be used to make a very secure system. I think this is where our effort should be focused, on making sure ISP provided hardware has these options available to parents. It makes much more sense than trying to force this on all endpoints.

If you have a firewall then make yourself a new network and block it from accessing the internet. Then you can use the smart features that your TV might have, such as powering it on/off, controlling it with Home Assistant, etc and also feel safe knowing that can’t happen again. Hope your replacement TV comes with the older firmware and you get another go at it.

If you ever decide to set aside time to tackle a re-install, you should consider setting up a file system that supports snapshots, or since you’re used to only using flatpaks, an immutable distro. Then you won’t fear updates because you can easily roll back as if they didn’t happen.