Mark brings up a good question, whose answer has been debated in dozens of threads.
You know how Jacques Cousteau would bring up a cannon which had been in salt water for 500 years, and it was in good shape? You need oxygen to have metal oxidize.
So, in theory, if one put calcium chloride, or sodium chloride in a water solution into their tire, and the fluid entirely covered the rim at all times, you would in theory never experience rust. Several guys have weighed in on this theory with their experience.
Now, it would seem that if one used a tube, the metal would be even better protected, right?
But, we all get punctures, and that fluid leaks out of the tire in the case of tubeless, exposing the rim to air plus corrosive salt, you have rust. With tubed, the fluid could leak between the tube and tire, and work its way to the rim and you have rust.
Not to mention that leaking salt all over your sod is a bad thing.
So, salt is old school. What about a more modern non-freezing medium - say old car anti-freeze. Ethylene Glycol is pretty poisonous, and corrosive if it's from a radiator where it has become acidic.
So, how about more friendly alcohol based solutions? Windshield washer fluid? Kind of expensive, and weighs less than the chlorides per gallon. It can be mildly corrosive, whether tubed or not.
Propylene Glycol? (RV Anti-freeze). It's non-toxic, but a gallon of -100 degree stuff costs $27.
Plain old water? Maybe if you live in south Florida.
RimGuard? Beet juice. Non-toxic, non-freezing, and heavier per gallon than the chlorides. But you can only get it at a dealer. Perfectly safe, tubed or not.
Now, whether to tube or not as it's own issue. Let's say you are not going to liquid ballast. If you are using a metric tire on an old SAE rim, you may have trouble getting the bead to seat. Firestone tri-ribs and Vredestein V61s in 16x6.50-8 are none to be problematic, and a tube just makes life easier. If you plan to run slime, I feel it is better to use a tube as it is less messy than non-tubed should you wish to change tires.
I tube. Just my preference.