FLA batteries are the dinosaurs of the battery world! AGM and Gel batteries are the new and better batteries. No doubt LiFPo batteries are now the new way to go, but these for sure need the proper charging voltage, which is why you need a DC to DC converter to use them in the RV world so you don’t destroy them. I’m just starting to learn about them. But at $800-$900 each it will be along time before I consider one for my type of use.
When the MH house batteries are due I’ll be going with AGMs.