TLDR: Forget the networking stuff, that's only a symptom. Call the power company and report a power outage, tell them "Lost Neutral". When they ask, don't talk about other symptoms other than "my appliances keep frying". DO NOT tell them a story. They will tell you to call an electrician, which won't work, you tried it.
You have a lost neutral on your AC power! Get it fixed for free!
The reason everyone's missing it is that they're focusing on your networking and not your AC power supply. From here on out, forget the networking. Focus on your broken AC power.
In the USA, we get 2 hot wires and a neutral. The 2 hot wires are 240V apart. The neutral is in the middle (or it's supposed to be) giving us 120V, twice, in two "poles". When the neutral wire breaks, we still get 240V, but the poles are not 120V anymore. Neutral starts wandering all over the place. So it might be 100V/140V, 90V/150V, 60V/180V, it varies.
The insidious thing about Lost Neutral is that usually, the voltage deviations aren't that bad. So everything still works. It just becomes subtle gremlins.
house lights and appliance started to act up - lights dimming or brightening when other lights or appliances in use
Yeah. "or brightening". That's what we're talking about.
Normally, this doesn't get too extreme, because neutral current has a couple of alternate paths. Each of yours had a problem, though!
First, at your house's main panel, neutral is bonded to ground which is wired to a Grounding Electrode System (GES, i.e. water pipe clamp or grounding rods) which ties to the actual dirt. So neutral current will try to go out your GES, through the actual dirt, to a neighbor or transformer's GES and then back to neutral. Dirt isn't a very good conductor (that's why we bother to mine copper), so it still allows a fair bit of wobble. Now you were mentioning
electrician came out, discovered by ground was cut when I recently had whole house re-pipe with flex, fixed that, re-grounding the electrical
Right. You had a water pipe GES, which was broken when converted to plastic pipe - common problem but still negligent. The electrician fixed you up with a different type of GES, probably ground rods and advised you to "mumble mumble" lost in the noise.
The second path is cable TV, typically grounded at both ends for safety. Neutral current will try to seek through that. Of course it's not rated to return 20 or 30 amps of current, so this happens
Internet & cable went out, called service repair, cable guys noticed the HDMI & COAX were hot (22-62v)
Varying, huh? That's typical of Lost Neutral.
added new grounding(?) connector for cable COAX incoming to house, BUT HDMI still hot on every TV or connection, new or old wiring
Right. Because the cable guy gave up on you ever fixing your Lost Neutral problem, and simply disconnected your cable TV cable from ground on your house's end. You do not have their permission to use their cable jacket as a substitute for your AC power neutral.
You are saying "the cable TV wire is hot" - probably not. Probably, the cable TV wire is properly grounded. Your house's grounds are hot because of the Lost Neutral.
checked all outlets, all 'correct' 120v reading
"Correct"? So you're using a dumb "pass/fail" tester that doesn't actually give you a voltage number. It just says "In the neighborhood of 120V" or "not". So it will read "correct" even if your house has a Lost Neutral. We need to get you a better tester. An excellent tester for all sorts of things, way beyond voltage - is the "Kill-A-Watt" home energy monitor. About $25 and Walmart stocks it. Just plug it into any outlet and it will readout the voltage. Now check several outlets and watch for that "high/low voltage" symptom. 100/140V etc.
What actually happened
If you look at an electric line from the poletop to your house, you will see an aluminum carrier wire with 2 insulated wires wrapped around it. That stuff is triplex. The bare wire is the physical carrier wire that carries the weight of all the wires. Unfortunately, it's also neutral. It whips in the wind for 30 years, and aluminum has no fatigue limit. SNAP! This is often (but not always) seen by an obvious gap and the cable hanging by the 2 insulated wires. That's a hard failure, and it's more likely on the neutral than the hots. (unlike an underground installation where it's equal chance).
Get it fixed for free today
Anyway, 95% of the time, a Lost Neutral occurs in the zone that the power company is responsible for maintaining. That overhead line wire. You call them up and report an outage, they send an insulated boom truck and it's fixed in a jiffy once the lineworker spots it.
When I called to have ours fixed, on a Sunday, they were out in an hour. They identified a neighbor's lost "hot" and fixed that too.