2002 gen 1 weird coasting noise

What a coincidence. I was having some noise in coasting and in drive "B".

Since that is associated with regeneration I decided to change the tranny fluid. The fluid I drained looked very old, there was a good bit of gunk in the drain plug, but nothing metallic, and that was a good sign.

With the new fluid in, the noise totally went away and the car drove quieter and smoother than it ever has since I bought it.

I am pretty certain it isn't your CV axles, and don't go getting concerned about mechanical issues in the CVT/Generator assembly.
Try this fluid change first. If you DIY it, it will only cost you for the fluid (5 liters or quarts) and a couple of 18mm x 24mm drain washers for the drain plug and filler plug.

 

I understand and look forward to listening to the video.
I am very certain, by all of the details you have given so far, that you are dealing with what I just shared with you to do.

My first response to the noise my car made was a concern that there was something mechanical going on inside the eCVT/Generator, or something in the CV Axles. The noise was a ticking tapping sort of sound and did sound very mechanical.

CV joints get particularly noisier in steering than in acceleration and deceleration, and also as CV Joints wear they begin to create a vibration that feels much like a tire or wheel going out of balance or out of round, so that rules out CV axle issues.

There could be an actual mechanical issue inside the eCVT/Generator, such as a broken piece in the Clutch/Damper assembly that would make that sort of sound, but it is very rare, and frankly, quite unlikely. And besides that, I would rather take care of the little stuff first such as changing the fluid, and seeing what that does, before preparing to jump into deeper mechanical issues that may not, probably don't, exist.

So many times I have personally been advised, definitively, by others on this site and other sites, many times, that an issue I am dealing with is some major pump or other expensive component, or Hybrid Battery assembly. And so far, I have always discovered that the issue can be solved or repaired by some form of servicing. If I had bought into their advice, like so many less mechanically experienced people than I am do, I would have un-nessicarilly spent many thousands of dollars more in the restoration of my Prius than the several hundred dollars it took to do the simpler DIY servicing that it actually needed instead.

Now I am an advocate to try to inform and guide people to check into and service the smaller related conditions around any component or Trouble Code, BEFORE becoming convinced to go to, replace, or repair the major component.

 

What error codes come along with your red triangle light? It's not a hifi A/V production, but my off-hand guess is that you'll be looking at doing a new wheel hub (or two).