Can a monk-barbarian benefit from Reckless Attack & Rage damage if he chooses Dexterity for his attacks?

Question

A barbarian, while raging, gains a damage bonus when striking with a "melee weapon that uses Strength".
He can also gain advantage to his attacks for the turn when he chooses to attack recklessly with a "melee weapon that uses Strength".

A monk, while using a monk weapon, can choose to use Dexterity instead of Strength for his attack & damage bonus.

Technically, most melee monk weapons (such as a quarterstaff) use Strength by default, so if a monk-barbarian, who wields a Strength-based weapon, decides to use Dexterity instead, can he still benefit from the Reckless Attack feature and the Rage damage bonus ?

Answer 1

No, because the weapon isn't using Strength any more.

Down in the Making An Attack section (PHB p193-194) we get this...

Ability Modifier. The ability modifier used for a melee weapon attack is Strength, and the ability modifier used for a ranged weapon attack is Dexterity. Weapons that have the finesse or thrown property break this rule.

ALL melee weapons use Strength, by default.

The rule for the Finesse tag on p147 says...

Finesse. When making an attack with a finesse weapon, you can use your choice of your Strength or Dexterity modifier for the attack and damage rolls.

This gives you an exception....you may use Dex instead of Str when using a Finesse weapon.

the rule for a Monk says

You can use Dexterity instead of Strength for the attack and damage rolls of your unarmed strikes and monk weapons.

Emphasis Mine to show that using Dex instead of Str is optional for a Monk.

Notice how similar the phrasing is between the Finesse rule and the Martial Arts rule.

Specific over General

The fact that the general rule for melee weapon attacks is "Use Strength" with the specific exception that "Finesse Weapons break the rule," coupled with the fact that the Barbarian class description has to explicitly say:

When you make a melee weapon attack using Strength, you gain a bonus to the damage roll...

despite the fact that all melee weapons use Strength by default makes it pretty clear that, in order for the Rage damage bonus to work, you have to actually use Strength for your attack/damage roll. Otherwise, it would work with Finesse weapons used with Dex, too...and the call-out that it must be a melee weapon that uses Strength is meaningless.

Answer 2

No, because that is not what the PHB says.

When you make a melee weapon attack using Strength, you gain a bonus to the damage roll that increases as you gain levels as a barbarian, as shown in the Rage Damage column of the Barbarian table.
- PHB p18

Emphasis mine. It doesn't say using a weapon that uses strength. It says when making a melee weapon attack using strength.

Answer 3

No

If the requirement for Reckless Attack were a non-finesse weapon, this would work, but it explicitly calls for attacks made with Strength.

However, you can use all Monk attacks with Strength without any penalty or limitation.

Answer 4

According to the 2019 Sage Advice Compendium, unarmed strikes are melee weapon attacks. You could just opt out of using Dex with the monk because it says you "can" use Dex, not that you have to do so. The monk will allow the unarmed strike to use a d4, and as normal you would just add your Strength mod. Now if you Rage, you are making a melee weapon attack using strength.

Can a monk use Stunning Strike with an unarmed strike, even though unarmed strikes aren’t weapons?

Yes. Stunning Strike works with melee weapon attacks, and an unarmed strike is a special type of melee weapon attack.

The game often makes exceptions to general rules, and this is an important exception: that unarmed strikes count as melee weapon attacks despite not being weapons.