Several of those old portables had tv tuners. None of them work anymore, at least not the USA.

There is a project out there that transmits video on UHF or VHF over short distances, basically a work around for old analog tuners. Basically hook up a video source and it will encode and transmit so you can watch stuff on gadgets with these old tuners.

Also, I don’t recall if they all have the a/v in functionality like this one, but that provided another option for using the thing as a monitor for other things.