A maintainer charger can go under the hood out of sight and be plugged into the 120 outside. Just use the clamps set of wires instead of the cig plug set.
IMO having its own charger like that is better than paralleling the starting battery with the house battery in case they have different specified floating voltages.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.