https://www.lambro.net/product/4-dryer-vent-seal/

It is attached to the house with either nails or screws thru the flange that is buried under the siding. You could just bust it up with a hammer and take it out piece by piece.

I would replace it with another one just like it. Only paint the new one to prevent UV degradation of the plastic.

I have that exact same vent. It is The Best dryer vent that i know of. Yes, it is ugly. But it is so much better than those flapper seal vents.

I still need help with this. The screws that attach it are under the siding.

"You could just bust it up with a hammer and take it out piece by piece."

That was in the answer above your repost. That is about the only way, shy of removing the siding.

How do I get the screws out?

Either unzip the siding or cut it back enough to expose the screws.

This is how I ended up mounting mine. How I did it is not THE way to do it & I don't remember why I did it this way. Anyway, it worked and it is on the back side of the house so I don't really care that it is ugly.

This was a two piece mounting block that I bought for the job & I remember cutting & fitting some plywood into the backside of the mounting block to give me something solid to anchor to. Glued it in using OSI QuadMax.