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Normally speaking, a Hand Crossbow has the Ammunition and Loading properties. Respectively, these properties mean that

• A free hand is required to use the crossbow and load it with its ammunition,


• When making an attack, only one attack may be made per action, irrespective of any features like Extra Attack.

The Repeating Shot infusion, available to Artificers with the 2019 Artificer Unearthed Arcana, lessens both of these restrictions:

This magic weapon grants a +1 bonus to attack and damage rolls made with it when it's used to make a ranged attack, and it ignores the loading property if it has it.

The weapon requires no ammunition; it magically produces one piece of ammunition each time you make a ranged attack with it, unless you manually load it. The ammunition produced by the weapon vanishes the instant after the it [sic] hits or misses a target.

—Repeating Shot, Unearthed Arcana: the Artificer Returns, 2019-05-14

Conversely, the description of the Ammunition property strongly suggests that the free hand required is necessary only because of the requirement to load the weapon with ammunition:

Ammunition. You can use a weapon that has the ammunition property to make a ranged attack only if you have ammunition to fire from the weapon. Each time you attack with the weapon, you expend one piece of ammunition. Drawing the ammunition from a quiver, case, or other container is part of the attack (you need a free hand to load a one-handed weapon).

—Weapon Properties, Player's Handbook, pg. 146

Now, knowing that this is considered playtesting material, I'd like to ask relative only to this specific revision of the material: does this mean that the user of such a weapon no longer requires a free hand to load the weapon, since the weapon no longer requires ammunition? Would the user of this weapon be able to put something like a Shield in their off-hand when using this weapon?

Repeating Shot causes the crossbow to ignore the Loading property. Therefore, so can we. The Ammunition property states that you need a free hand to load a single-handed weapon, but Repeating Shot makes clear that deciding to "manually load it" is optional. Thus, if you decide not to manually load it, there is nothing in the Ammunition property that would require you to have a free hand.

It looks like you're clear here. Enjoy your shield (or whatever).

Happily, this was directly addressed at about 15:00 in the 6/05/2019 Dragon+ Q&A with Jeremy Crawford.

Jeremy Crawford: It says you need to have a free hand to reload a one-handed weapon. Well, it stands to reason that if you don't need to load ammunition, you don't need that free hand to load the nonexistent ammunition. So the short answer is, you do not need to keep your hand free to load ammunition that you don't have to load. [...] Do whatever you want with that other hand.

That's straight from the main rules guy for the game in an official Q&A session, so it's as clear and definite an answer as you're going to get short of actual rules text.