Maybe quick, but not cheap.
Mentioned a few years ago is HDMI or IP to RF modulators.
Terra IP to RF modulator MI520
There's other brands too.
Make sure your model is suitable for your country's TV transmission standard. E.g. New Zealand is DVB-T.
These wire into your TV antenna distribution wiring so that every TV in the house sees this video feed like a standard TV channel.
In my household I haven't used my HDMI to RF modulator in years. It's a great device but I hardly had a use for extra monitors around the house when my office has a cctv monitor.
Modulators also introduce some lag (dependant on decoding lag of your TVs too).
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