And the local shows ( those only shown in certain areas ) are also very much long gone; sadly. :-(
Not as entirely bad as that. “Margie,” “Riley,” “Joan,” and even “I Led Three Lives” do actually survive, although I don’t think any have been re-mastered from their 35mm sources. MGM/UA seems to now have control of the Ziv library, and they did re-master a number of their series, although perhaps not the older ones, like “I Led Three Lives,” “Boston Blackie,” or “Mr. Distict Attorney” (at least, to my knowledge). Weiss-Global used to syndicate “Joan,” and they had the whole run in 16mm in syndication back in the 1980s/90s. I think Fox owns the rights to “Life of Riley,” but I don’t know how on earth that might have happened.
But, when you get to “live” series of the 1950s, or “taped” series of the 1960s (like game-shows, soap-operas), the majority is long-gone. In the early-1950s, there were also a lot of filmed series that were independently-produced, and I suspect many of those are semi-lost. Shows like “Front Page Detective” or “Cases of Eddie Drake,” and things in that vein, where a few scattered 16mm prints circulate amongst collectors, but whether the original elements still survive is likely a big question mark.