I think you will need to turn the sofa up side down to determine where you can
bolt on " L " brackets, 4 would be best . I would shop at Lowes or Home Depot
for L brackets and some rather large lag bolts , maybe 3/8 or 1/2 inch
At the same time you could install seat belts if they are not already there .
We had 2 sofas in our coach so we removed one of them and installed 2 euro
recliners . We use the seat belts to secure those recliners when we travel .
You may be able to secure your sofa with seat belts .
Our dining chairs are not secured they just sit there never moving .
I have found things don't move around except when I made a really hard stop
then a few things move a little .