Scholars have not ruled that such acts are haram because they do not violate any laws of Shariah. In fact many would consider them recommended of they remind people of the tragedy of Karbala and bring people closer to the values of Karbala.

The reason why they use drums is to show support for the family of Imam Hussain (a). In Karbala more than 30,000 soldiers appeared to fight the Imam. Many of them had drums or other things. They are called the drums of war. They would strike them to signal their preparedness to fight the Imam. This scared the women and children. So today people do that to symbolically say “we are with you, here are our drums to support you…”

As for the things they do for al-Qasem, it’s also symbolic and represents him being a young youth and about to get married. Sometimes they’ll even replicate aspects of a wedding to show their love for al-Qasem and that he was denied the opportunity to have a wedding because he got killed.

You can share with the articles on the history of military drummers.

Such as this one:

https://www.napoleon.org/en/magazine/publications/marching-to-the-drums-a-history-of-military-drums-and-drummers/

Or this:

https://en.m.wikipedia.org/wiki/Drummer_(military)

https://en.m.wikipedia.org/wiki/Military_drums