At first it was just the antenna and HDMI and later, just one at a time. I haven't seen this feature making a comeback.
Check out switchers and multiplexors like https://www.amazon.com/dp/B01BV1XBIY/
I am looking for a tv that will allow both cable and directv in put and show split screen one on each side. I have a samsung, 10 years old, that does that now but cannot find a new one

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