Hopefully you got it to work by now but since I was also stuck on this and want to save future googlers the hassle Let me tell you what I did. I used the documentation of V3 where the MenuController is actually documented. It seems you have to enable menu’s if you want to have multiple menu’s from the same side.
I do it like this:
constructor(private menu: MenuController){}
async openMenu(menuId: string) {
await this.menu.enable(true, menuId);
await this.menu.open(menuId);
}
now if you call openMenu with the menuId it actually does open. Good luck to anyone finding this.