If you have the hitch tabs hanging down already, you can weld up something like this to bolt on. Keep in mind you will need accurate measurements as the tabs may not be exactly parallel with the frame.
Also check out a company called Mount-n-Lock. They have a hitch that bolts onto the bumper, but also have what they call "safety struts".
The safety struts bolt to the frame of the RV and keep the rear bumper from being able to twist. I used them for a bike rack on my Jayco with no movement at all.
When I traded for the Elkridge, they came off and went onto there for the bike rack. I highly recommend them myself and they are very well made.
On our 3160EL, I had a custom made hitch installed. While I use it to carry a WR450 drit bike, the concept of having 2 inserts vs 1 is the secret sauce. You will avoid ALL rocking and movement. I also use this rack to carry 2 Rad Electric bikes (when we're not camping in location we can ride dirt bikes). Each Rad Electric bike is about 80 pounds and this carries those with ease. I opted to have a standard insert for the middle, just in case I need a "normal" hitch usage.
FYI, every bike rack I found, usually has a warranty exemption in the fine print, that voids the warranty if used to haul bikes on an RV. We had a lot of issues with our bikes on a receiver on the back of our 3260. It got bounced so hard we lost our bikes twice. So I re-enforced everything, with added steel and welding and it still broke. Ended up we put a receiver on the front of our tow vehicle, not a problem since. Not every fifth wheel bounces that bad, it has to do with the axle placement on the unit.
You should ONLY use a 2 inch receiver hitch for carrying bikes. As noted in previous post by Sengli, almost every bike rack manufacture will void any offered warranty if carried behind an RV. I also lost bikes using the factory supplied 1 1/4 inch factory supplied hitches that were the only size the factory offered years ago. Today the new Bighorns can be ordered with a 2 inch receiver and supports up to 300 lbs. When I was researching bike rack companies 2 years ago and speaking to their engineering departments, only 1 bike rack manufacture would warrant their rack for installing behind an RV. That rack is made by Swagman. It is extremely well made and is 2 inch.
Swagman makes a RV rated bike rack. It is rated for 2 Electric Bikes at 60 lbs each. I have a Rocky Mountain 29'er mountain bike (20 lbs) and the DW has a 26 inch hybrid bike (25 lbs). No issues in 2 years and 10,000 km of travel. This will be going on the new Landmark as well. This is a 2 inch receiver mount too.
Be careful adding a hitch for bikes. We have a 2020/21 Wilderness Travel Trailer and wanted to add a hitch to carry 4 bikes on our trips. We took the trailer to a welder who added a hitch, supported it with strong gussets, and re-enforced the connection of the bumper to the frame. To make a long story short, all of the welder's modifications held great, but the bumper material itself was not strong enough to support the weight. One of the gussets sliced through the bumper and the top of the bumper on either side of the hitch simply tore apart. Our bike rack fell to the highway (still attached to the bumper but dragging). No one hurt. Bike damage limited to one tire. But scary. We took the trailer back to the welder who removed the bumper and replaced it with a much thicker gauge (at no extra cost since he felt bad about misjudging the strength of the OEM bumper). Total cost to us $300. Looks really sturdy. I don't know why they make the bumpers so thin, but I definitely encourage a full replacement of the bumper if you are trying to add a hitch.
I don't know if this is a already-closed-thread but I just want to share what bike rack work for my Heartland 2012. Of course roof-mount is not an option. 2" hitch type bike rack is fine but just please be mindful that you need to show your plate number clearly as some state required it. I got mine from an online automotive parts store in NY, a Thule brand that can hold 3 bikes.
If you are still considering roof top, please be careful on vertical clearances on your place.