In 2017 there was a playtest article written for Mass Combat.
Copied from the PDF
This Is Playtest Material The material here is presented for playtesting and to spark your imagination. These game mechanics are in draft form, usable in your campaign but not refined by design iterations or full game development. They aren’t officially part of the game and aren’t permitted in D&D Adventurers League events. If we decide to make this material official, it will be refined based on your feedback, and then it will appear in a D&D book
Longer answer: They did come up with the board game aspect of dragonlance, which is meant to represent larger combats. I've not played it, but I understand its largely scenario-based and tailored to the specific set pieces in the campaign. But I'm sure there are folks out there trying to kit bash something into a more free-form version.
Beyond that, there are some 3rd party versions of mass combat.
In 2017 there was a playtest article written for Mass Combat.
Copied from the PDF
This Is Playtest Material The material here is presented for playtesting and to spark your imagination. These game mechanics are in draft form, usable in your campaign but not refined by design iterations or full game development. They aren’t officially part of the game and aren’t permitted in D&D Adventurers League events. If we decide to make this material official, it will be refined based on your feedback, and then it will appear in a D&D book
Has anything gone forward with this since then?
Short answer: nope.
Longer answer: They did come up with the board game aspect of dragonlance, which is meant to represent larger combats. I've not played it, but I understand its largely scenario-based and tailored to the specific set pieces in the campaign. But I'm sure there are folks out there trying to kit bash something into a more free-form version.
Beyond that, there are some 3rd party versions of mass combat.
Way back in the day, I and others had good times using "Battle System". Is that the kind of thing that Mass Combat is intended to replace?