I might consider a tarp IF:
It did not have grommets - some of the good nylon tarps from Kelty and Kondos have fabric loops (stronger than grommets too). You think dirt will abrade you should see what a nice big grommet will do if whipped by the wind on a flapping tarp. Expect to pay $100 and don't expect years of use, tarps are not intended for 24/7 365 use.
I had a solid post, tree, or heavy bolted anchor point for a ridge line over the camper. Tent poles won't do the trick because poles being flung into camper by wind would be bad. If tarp is directly on the camper the abrasion factor exists AND it won't be shedding any snow load so run with a ridge line that keeps the tarp off the camper is a requirement.
I'm able to provide solid anchor points in the ground for all lines. Lines attached with bungee cord or other mechanism that has some "give" so the lines don't break and the tarp does not rip.
One can remove the grommets from a cheap poly tarp then use a ball to do tarp attachment. Sometimes called a monkey fist. I would not use a rock! But a rubber ball should work fine. Then at least if the tarp breaks free you don't have to worry about the grommet or pole beating the side of the camper.
I have actually given some thought to setting some 4x4 or 4x6 (groan heavy!) poles into holes with concrete to use as anchor points for a tarp. Still sort of at the mulling it over stage. Not the break out the post hole digger and get a grandkid to come over stage.
That is the one other method of attachment for a tarp I would consider pinning tarp edge between to pieces of framing lumber and screwing them together. Used all the time to lay poly tarp on unfinished roofs.
For now I'm going with the thing is water proof right? So why does it need to be indoors? I know I know it is better but.... need?