It is sewage. Rip out the carpet. And be prepared to cut out the paneling if it is wet.

Did you call your insurance company? They should pay for professionals to do this for you, Service master can be there in an hour. Not cheap if it's not covered, but who wants to deal with this?

What’s that fat pvc pipe that drains into the hole in the video?

In my old house that was the drain collector for all the baths and kitchen = sewage. It is needed if the house is below grade if the sewage system or too low for the septic tank.

Doesn’t look look like ground water piping. Where would the sewage go if it’s not in that closet?

If I’m wrong that’s great.

Should still call insurance.

Radon? Removed by a sump pump/ blower contraption?

Not sure I'm supposed to feel good or bad about being wrong on that one.

I'm glad I moved out of the midwest before they came up with that craziness.

Should still call the insurance company ASAP.

GL!