Block sky light from inside RV

It depends whether you want some light through or to completely black it out.

Amazon has insulators that fit right into your skylight.

Or a cover you can install.

Just a few options.

My wife just stuffs a throw pillow in there. lol

I bought a used trailer and it looks like the previous owners applied a very dark tint film over the skylight. It does allow some light through. Might be an option depending on what you’re looking for.