When I bought a cheap HD receiver for the kitchen TV, although it allegedly 'looped through' the main RF feed from the antenna to the TV, insertion loss was just sufficient to cause pixellation. So, for about £25 from currysdigitaldixonscomet (or whatever it's now called), I bought a One-For-All SV9542 amplied signal splitter which has a variable gain control and 4 independent aerial outputs, which did the trick.
This link
https://at800.tv/ may confirm whether or not 4G interference is likely at your location.