I know it's a optional rule, so not all campaigns play with Disarm option during combat.

But has anyone had experience with this in gameplay with a monk? Are the Unarmed Bonus Action or Flurry of Blow Unarmed strikes valid uses for an attempt to Disarm someone?
I don't see any rules saying otherwise, but curious on people's experience.

Page 271 of DMG

Disarm

A creature can use a weapon attack to knock a weapon or another item from a target’s grasp. The attacker makes an attack roll contested by the target’s Strength (Athletics) check or Dexterity (Acrobatics) check. If the attacker wins the contest, the attack causes no damage or other ill effect, but the defender drops the item.

The attacker has disadvantage on its attack roll if the target is holding the item with two or more hands. The target has advantage on its ability check if it is larger than the attacking creature, or disadvantage if it is smaller.

I have no experience with the disarm optional rule, but your bonus action attack or FOB attack qualifies because your unarmed strikes are weapon attacks. A melee weapon attack specifically  

If the rule said make an “attack with a melee weapon”then it wouldn’t. 

Weird I know, but that’s the distinction the rules make. 

Whether or not this is a good tactic I don’t know. Seems like you might be better off doing something else with your attack. But if it’s a specific situation you need to get an item out of the BBEG’s hand then it’s up to the DM if they allow it 

Thanks for the feedback, ThriKreenWarrior. I figured that was the interpretation that the bonus action unarmed strike could be used in this manner.

I bring this up, as that there are situations where the opponent we are fighting has an exceptional AC from Armor that I might struggle to hit. Being a hybrid character with a non-optimized Dexterity Attack roll, I wonder if it is worth using my unarmed strike to do something more disabling, like knocking their weapon out of their hand.  IE: It's harder to hit a high AC of 21 or 22, but if it is a Roll vs Roll, my chances seem better off at trying to attempt to disarm them.

We used it. Was fun. Remember that the creature can just pick up the weapon as part of its movement or action for free. So don’t forget to have a plan to get that dropped weapon away from that creature before their turn. 

...so I need to revisit this, as I think I may have found a loop hole that I didn't know existed...  I believe Stunning Strike and Disarm stack ontop of each other.... Option rules for Disarm are "use a Weapon Attack"... and Stunning Strike is also ""hit another creature with a melee weapon attack."

I believe in short, you can use a Disarm Attack and also apply Stunning Strike at the same time.. correct?

Stunning Strike

Starting at 5th level, you can interfere with the flow of ki in an opponent’s body. When you hit another creature with a melee weapon attack, you can spend 1 ki point to attempt a stunning strike. The target must succeed on a Constitution saving throw or be stunned until the end of your next turn.

I’m not sure if they would stack.

The disarm, I believe, would have you state before attacking that you are trying to disarm and then you roll your attack and they have to beat your roll with a skill check (athletics or acrobatics). It’s not an actual attack vs AC.

And stunning strike requires an actual attack that hits the target (attack vs AC)  Edit: although it doesn’t require that you do damage 

But your DM might allow it since it is situational. I don’t think it’s a combo that breaks the game. 

Hmm... good point about the "HIT" (attack vs AC) wording. In the end, I agree it'll be a DM ruling or house rule