1. Try an RCA ground isolator (try on different components to see what works), e.g. https://smile.amazon.com/InstallGea...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==Of course I know something is wrong.
My unstated question should have been, what can be done to safely eliminate hum when it’s associated with AC ground pin connections? What’s the cause and what’s the cure? This stuff is all supposed to work correctly together as provided, but it doesn’t. Am I expected to install isolation transformers at every connection? I just want to know where the fault is and how to fix it. And of course some of the components have no ground pin, including a new Sony 4K TV.
2. Try a cable isolator (cable is notorious for introducing ground loops), e.g. https://smile.amazon.com/Ground-Loo...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
3. Try an AC (power line) isolator, e.g. https://smile.amazon.com/Ebtech-Hum...X&qid=1654439417&sprefix=hum-x,aps,107&sr=8-4
There are many examples of each, just grabbed what came up in a quick Amazon search. I would start with an RCA and cable isolator and see if those work first. Put the cable isolator in line nad see if that fixes it. If not, you can leave it, and try the RCA isolator on different components. You may want to start by pulling components one at a time (including the cable or cable box) to see if one of them makes the hum go away, then you can isolate just that component.
HTH - Don