Press the button to turn off the power strip when you're not watching it.

The other solution for those who have a flat white wall (or are willing to install a projection screen) and which I used for years and years: use a dumb projector. There are plenty of perfectly fine dumb projectors and they're very cheap too (compared to the equivalent TV). This also made for the largest diagonal I ever had, in a huge living room, which was really great: basically turning the living room into a mini home theater. I painted the walls etc. accordingly, including a special paint for the white projection wall and black for the side and back walls. This was a better experience than any $$$ TV.

Sadly atm I can't use my projector for my wall ain't flat and I can't install a projection screen and I've got nowhere to put my projector: I could use a short-throw one but the place ain't mine and I'm not allowed to drill holes etc.

So atm it's... Pressing the button on the power strip that powers the LG TV. I know, I know: doesn't help much when the TV is on.

Next thing to do is separate all the junk devices (TV, smartphones [the ultimate spying device btw, much more than your TV], smartwatches, tables, etc.) from your proper stuff (e.g. your important PC running Linux/FreeBSD/etc.). I use different physical LANs (and a bridge/router) but VLANs would do too.

Many cheap home routers also by default offer at least a "guest" network: a perfect place the TV and your relatives' devices when they visit and want access. Set usage quota on the guest network too.

At some point all these devices shall use other networks than yours, so you'll be sorry out of luck anyway. But as long as they don't come with their own battery, pressing the button on the power-strip is some kind of giant low-cost "hack this" middle finger.