Hi @Anonymous User
Using an Xbox One or Google Chrome Cast dongle should work with your Panasonic television.
Because you mentioned the picture is pixelated, it sounds to me there is some sort of internet or wifi issue or problem with the NOW App rather than the Panasonic TV HDMI connection.
With regards to the Xbox can you use it over Ethernet and what down internet speeds are you getting.
Also try a fresh NOW App download and a reboot on your Router.
If using wifi try a different wifi channel and if your Router is dual band try both 2.4ghz & 5ghz.
And yes NOW have blocked for a few years now using a HDMI lightning connection between your iPhone NOW App and television.