Instead, I want to know what sort of things would cause brand new, sudden and massive RF interference?
I've had my setup going on for several years now without any RF interference.

There is nothing new about my setup.
But tonight, I was fixing some URC code setup stuff.
And my area is going through an unusual deep freeze weather-wise.
Those are the only two anomalies.

Suddenly, my RF went all to hell.
One second I was making progress on fixing some codes.
And the next, my RF indicator light was going full blast, non-stop.

I broke out my spare MRF-350 and RFX sensor and walked around the house, plugging it into various wall outlets to check locations in the house.
Every single square inch of my house is suddenly flooded with RF.
I've never had this issue before and there is no new equipment or electronics or anything.

At ~6:59PM today it was fine.
And suddenly at ~7PM all RF hell broke loose.

I've un-powered all my computer & home theatre equipment but still had the problem.
In a day or two when it gets warmer, I'll shut off all the breakers on the power panel to test.

Edit: personal user, not a pro. This is my home setup

Things that can cause interference.... pretty much anything!
When caps go bad in equipment, the device may seem to still operate fine but the cap was filtering RF noise that is now broadcasting. Also triacs can start to go bad and cause RF noise. Bad electrical connections that are arcing, can cause RF noise.

So =
Your HVAC. Lighting dimmers. Battery backups. Microwave ovens. Ceiling fans. Computers. A/V equipment. Network equipment. Fluorescent lights. LED lights. EV car chargers (including golf cart chargers).
These are all things I have seen create a ton of RF interference before. Some of these things were 'working as intended' and others had issues that was causing the problem (listed above).

Since this is something that just started. And the fact you said you walked the whole house and the interference is everywhere. You'll be looking for a very high energy emitter that has a high duty cycle. Something like your HVAC. Do you have any large chargers plugged in (like for a car, golf cart, electric mower)?
Good possibility this could also becoming from your neighbors.
Do you live near an airport? Marina?

Also, is the interference actually causing an issue with commands not getting thru from the remote? If not, not worth worrying about is it's not an actual problem.

Just as suddenly as it started, it's now gone.
It abruptly started around 7PM last night and was going all the way through till I went to sleep.
But when I woke up this AM, it was gone!

The most out-of-ordinary thing near my house is a school about a mile away.
Everything else is houses, houses and more houses.

But last night was the coldest night of the year. So, I'm wondering if someone nearby kicked on a generator or something that introduced interference?

Hope it doesn't return.

FOUND THE PROBLEM.
Or at least, I narrowed it down to a particular device.

My URC KP-900 remote control is the culprit.
Went back to finish my programming today.
Noticed the KP-900 batteries were dead.
Replaced them.
About 15 minutes into a frustrating programming experience, I noticed that nothing was working again.

Sure enough, the RF LED on the sensor was lit up constant.

Thought about it a moment.
Pulled the batteries from the KP-900 and sure enough, the RF interference went away.

A minute later, I duplicated the same situation.

Gonna try a factory reset on the KP-900 to see if that helps.
It's a new-old-stock remote.

But what seems to be working is that I learned all the commands to an MX-980 and then used the Transporter function to copy those commands to the KP-900 and so far, so good.

Just taught myself the Transporter function.
It's super easy once you figure it out.

First time, a Samsung RF remote, paired to the TV, battery condition got low.  Client recharged the Samsung remote and all well.  Was sending Volume Up continuously. 😳

Second time, randomly was Volume Up again, different house.  Apple TV remote was the culprit. Recharged it and had to re-pair it.

Random.