How to keep bright light out of camper from skylights/vents/door glass

Just a few ideas from my experience - I made little curtains for door and all windows out of a very heavy upholstery fabric that blocked out alot. You can buy blackout fabric as well. And vents that were not in use I screwed aluminum vintage signs on in the interior (there were not appliances that needed venting on the interior.) I didn't have the skylight issue because ours are aluminum instead of clear plastic/glass. You could always use aluminum foil in them for a quick fix, alternately if you're parked a while a piece of vinyl with elastic sewn around it seems like it would work too.

You could get a film that darkens the light and windows. Its not too crazy expensive and you pretty much wash the windows, get them damp, put the film on and cut around to fit to size. We did that in our bathroom for privacy and its lasted years

Buy some room darkening vinyl. It's what they use on the back of room darkening curtains. They carry it at Walmart in the fabric department. If the windows or skylight have metal around them you can always buy a sheet of magnet and cut to size to fit over the openings.