The biggest problem is not the video stream being encrypted
The big problem is watch free is an App/service running on the TV , with out having a video output signal hdmi, analog,DIGITAL video? No device can record it, this would require a screen recorder app running on the smart tv while watching the movie
If the TV can output a video signal ( it needs a video out connector ) of some kind , then maybe a device could be found for recording,
I do have a device that records HDMI signal to usb thumb drive, this type of recorder could be used IF the TV has an HDMI output like cable boxes,satellite receivers, DVD players and my laptop some tablets and phones, but I have never seen a tv with hdmi out,
My Vizio has 3 HDMI inputs and 2 audio out, one analog, one digital audio out, on mine even the USB input is crippled it will only accept slide show image files thru usb, like Kodak format and jpeg pictures, I can manually display and move thru select jpeg pictures from usb stick, I have done this one time, no mp4 video or even old AVI video format allowed on the USB, I love my TV except for the useless USB plug, mine is not a smart tv,
To the OP
You can't record a signal that is only internal, unless you can some how modify the inside of the TV
Is there a DVR option for that tv,
I have a Mediasonic solid state digital TV tuner, video recorder, that will record OTA broadcast tv, or non encrypted cable, to usb thumb drive or portable hard drive, records .MTS files in 720p and 1080I and will play them, it does NOT do internet stream capture, I connect the HDMI recorder between the laptop and the TV when I want to record something from the internet, this is a manually operated system, not automated, not programmable, step one power up everything and get ready
Step 2 start recording
Then start playing the video stream on the laptop
Step 3 stop play of video on laptop, at end of video stream
Then stop the recording at the HDMI recorder