May be a moot point, but when you say "truck camper" are you talking about one that fits in the bed of a truck? If so, perhaps you can disregard the following because I know this company has a minimum value they'll work with ($35,000 I believe).
If you're talking about one that is "pulled by a truck" then read on, or perhaps others who have towable campers or motorhomes may be interested.
There is a company called "Pop Sells" (
https://www.popsells.com/rvs) that specializes in RVs and a sister-site that sells yachts.
We listed our Class A Georgetown with them and had some interest shown. There is NO COST unless your unit sells, then they charge 10% of the sales price. They do all the marketing and advertising at their own expense.
You are also allowed to continue trying to sell it on your own (but no other "listing service"). As it turns out, we eventually sold ours directly through Facebook MarketPlace - but we did have several folks showing an interest through PopSells.
It doesn't cost anything and it sure wouldn't hurt to have that second effort going.
When we listed with them we added the 10% into the sales price so our "net" would still be what we wanted out of othe coach.