4g lte. I'm curious on how you are going to Chromecast to the rear. I plugged in my Chromecast in the back and couldn't get it working in 5 minutes....then I broke it (fortunately just it and not the HDMI port).
I hooked up chromecast to my tv, from phone 1, setup a wifi hotspot.
from phone 2 connect to wifi from phone 1, added google home, found the chromecast, set it up to use wifi from phone 1. it updated and i could cast things from phone 2 to the chromecast on my tv in the house.
Then i went to the van
plugged chromecast hdmi into backseat display, and the usb cable for power into the same seatback that came with the chromecast.
Turned car on, when to uconnect theatre, clicked input, hdmi1, went to youtube on phone 2, clicked the cast button, and it showed up on the rear screen. while not moving, you can watch the content on the dash and click "listen in" to also hear the content from the van's sound system.
Worked like a charm, but I'm planning to replace phone 1 with the wifi hotspot from the van
I tried the mirroring of my phone with uconnect and it was SLOW AND LAGGY. So much that i just abandoned the notion to make it work.
Also I recommend this hdmi cable. Have not used it yet, but i'm hoping it reduces the risk my 4 year old will kick the hdmi plug of the chromecast and break it off in the seat. I think this is facing the right way. skinny end of the hdmi cable to the left, with cable hanging down.
HEY! i'll put it into the other chair of my 2 year old. Less likely to get broken off. Too bad there isn't a hdmi port in the front of the van.