mirroring

if your monitor has a hdmi input you can use a hdmi adapter and hdmi cable to connect to the tv like this Apple Lightning Digital AV Adapter

For an Apple device, you'll want to buy an Apple TV and then you can use native wireless display by swiping up from the bottom and choosing the Apple TV to display to. This will also work with Mac OS X computers. For an Android you'll need either a TV with Miracast built-in as well as a phone that supports it. You could also try buying a Chromecast dongle and using apps that support that. For Windows computers 8.1 and Windows 10, a miracast adapter also works, if you choose to buy one I would suggest the Microsoft version 2 miracast adapter or newer and not one of the cheap Chinese knockoffs.

If you want to display your iPhone screen on a monitor, you probably need an HDMI adapter for your iPhone. I'm assuming that you really do mean just a monitor when you say monitor. I just use my iPhone by itself and mostly just follow the verbal directions. If you want to look at the screen (any screen) for directions while you're driving, you're likely going to run into something.

Mirroring to what? The in-dash entertainment system? To do that the entertainment system needs to have Apple Car Play for an iPhone, Android Auto for an Android smartphone. In both cases this is relatively recent technology, found in the most recent vehicles and sometimes only premium models. Your RV might be new enough, but as a bargain-basement RV model manufactured for a single retail chain, the Freedom Elite might not have the most premium entertainment system. Aftermarket receivers with Car Play or Android Auto sell for about $400 to $800, depending on whether you are also buying satellite radio. Built in navigation pushes the prices to the $1000 to $1500 range, similar to costs when these are optioned as a feature on a car not having this as standard equipment.

I'm trying to deal with this now, car shopping. I'm finding that in order to get the "radio" with the features I want, I might have to buy a more premium car model than I would prefer, paying extra for a lot of stuff I don't really want (like moonroofs and heated seats, etc).

For what it is worth, even with Apple Car Play, you won't be using Google Maps. The only mapping application supported by Car Play is Apple Maps. To use Google Maps, you need an Android smartphone and Android Auto. Google owns the Android world.

Mirroring? Do you mean between an iPhone and iPad? I use a cable between iPhone or iPad and tv. Others use bluetooth with their smart tv.