DirecTV box setup

Hello - my parents have recently upgraded their old flat screen TV's to a couple of newer Smart Tv's (both Vizio brands) and prior to upgrading, the had their direcTV box hooked up to their bedroom and then it was also connected to the kitchen TV (this tv could basically just let you watch what was ever playing in their bedroom but no capability to change channel in the kitchen and whatnot, if that makes sense, it was just being mirrored to their kitchen TV so to speak). The DirecTV box is hooked up as it should be to the back bedroom tv, then a green/blue/red cable is connected from the DirecTV box to a RF MODULATOR box - where there is a super long coaxial cable that reaches all the way out to the kitchen tv, then that cord is connected to a "digital to analog tv converter" box where then another coaxial cord is coming out of and being directly attached to the kitchen tv. Before, this set up worked perfect! No issues, but now that we have these newer upgraded TV's, this set up will not work. These new smart Tv's don't just let you hit a number and go to a channel like the old ones did, so I am struggling to figure out how I can get this set up to work on these new TVs, if it is possible with them. I'm at the point of wondering if these new smart tv's just don't support this type of set up/mirroring with these converter boxes because they are so new and updated compared to older flat screens. Can anyone help guide me in the right direction with this?