Does the Tavern Brawler Feat mean you have to choose between Shield or Duelist?

Question

Tavern Brawler

Accustomed to rough-and-tumble fighting using whatever weapons happen to be on hand, you gain the following benefits:

• [...]
• You are proficient with improvised weapons.
• [...]

Now, this would technically turn a Shield into an improvised weapon, with which you are proficient, that deals 1d4 damage. Does this make the Fighter's Duelist Fighting Style incompatible with a Shield if you get the Tavern Brawler feat?

Duelist (Fighting Style)

Gain +2 bonus to damage rolls when wielding a melee weapon in one hand and no other weapon.

(Emphasis mine.)

Answer 1

By strict RAW no, it would not make it incompatible.

There are a few reasons for this:

1. Improvised weapons are not weapons per-se, they don't have weapon stats* and they are not listed in the weapon category.
2. The reason for the no other weapon in the description is for the two-weapon fighting and two-handed options, though the second one is moot for this question.
3. By a strict RAW** you cannot use two-weapon fighting since the shield is not a weapon (no bonus action to attack with a shield as an improvised weapon).

Duelist: Gain +2 bonus to damage rolls when wielding a melee weapon in one hand and no other weapon.

Two-weapon Fighting: When you take the Attack action and attack with a light melee weapon that you’re holding in one hand, you can use a bonus action to attack with a different light melee weapon that you’re holding in the other hand.

*- This question shed some light in this.
**- Crawford stated that the intention is that two-weapon fighting can only be done by using weapons.

Dual Wielder is intended to work with actual weapons. Using the feat with improvised weapons is up to the DM.

It is a DM decision on a more lax RAW interpretation.

As you can see, by strict RAW, the central issue is the two-weapon fighting feature. Therefore, if the DM consider that improvised weapon can be used with two-weapon fighting it is up to the DM to resolve this conflict.

Answer 2

I think the conceptual problem is here

Now, this would technically turn a Shield into an improvised weapon

which is inaccurate. An improvised weapon is defined on PHB 147 to be

An improvised weapon includes any object you can wield in one or two hands

A shield (which isn't a proper weapon) can be wielded, so it's an improvised weapon. How skilled your character is at using it as a weapon has no bearing on its weapon-ness, the way a wizard poorly wielding a greatsword is still using a weapon.

So, consider a duelist with a shield. They're holding a real weapon in one hand, and a potential improvised weapon in the other.

If the duelist also has Tavern Brawler, then they're merely good at said improvising; it doesn't fundamentally change the duelist-shield situation.

So, can a duelist use a shield and the Duelist style? The answer is yes, because the shield isn't listed in the Weapons table.