How do I make a trash can block that automatically void anything hoppered in.

Triggers are not applied to blocks
You must apply it to the GUI slot.

For the trigger, use Remove on the slot tab.

https://imgur.com/8fsU3tW

Currently, there is no way to recognize external slots in the MCreator, so you need to add custom code.

STEP1
code edit 'GUIName'Menu.java

SETP2
Find the appropriate code part.

    @Override

    public ItemStack quickMoveStack(Player playerIn, int index) {

        ItemStack itemstack = ItemStack.EMPTY;

        Slot slot = (Slot) this.slots.get(index);

        if (slot != null && slot.hasItem()) {

            ItemStack itemstack1 = slot.getItem();

            itemstack = itemstack1.copy();

            if (index < 1) {

                if (!this.moveItemStackTo(itemstack1, 1, this.slots.size(), true))

                    return ItemStack.EMPTY;

                slot.onQuickCraft(itemstack1, itemstack);

            } else if (!this.moveItemStackTo(itemstack1, 0, 1, false)) {

                if (index < 1 + 27) {

                    if (!this.moveItemStackTo(itemstack1, 1 + 27, this.slots.size(), true))

                        return ItemStack.EMPTY;

                } else {

                    if (!this.moveItemStackTo(itemstack1, 1, 1 + 27, false))

                        return ItemStack.EMPTY;

                }

                return ItemStack.EMPTY;

            }

            if (itemstack1.getCount() == 0)

                slot.set(ItemStack.EMPTY);

            else

                slot.setChanged();

            if (itemstack1.getCount() == itemstack.getCount())

                return ItemStack.EMPTY;

            slot.onTake(playerIn, itemstack1);

        }

        return itemstack;

    }

------------------

Change code

    @Override
   public ItemStack quickMoveStack(Player playerIn, int index) {
       ItemStack itemstack = ItemStack.EMPTY;
       Slot slot = (Slot) this.slots.get(index);
       if (slot != null && slot.hasItem()) {
           ItemStack itemstack1 = slot.getItem();
           itemstack = itemstack1.copy();
           if (index < 1) {
              if (!this.moveItemStackTo(itemstack1, 1, this.slots.size(), true))
                   return ItemStack.EMPTY;
               slot.onQuickCraft(itemstack1, itemstack);
           } else {
              if (!this.moveItemStackTo(itemstack1, 0, 1, false)) {
                   return ItemStack.EMPTY;
               }
           }
          
           if (itemstack1.isEmpty()) {
               slot.set(ItemStack.EMPTY);
           } else {
               slot.setChanged();
           }
           if (itemstack1.getCount() == itemstack.getCount()) {
               return ItemStack.EMPTY;
           }
           slot.onTake(playerIn, itemstack1);
       }
       return itemstack;
   }
 

https://imgur.com/qr5UEu5

Oh, I got it wrong
There was a mistake because I was using a translator.

Without modifying the GUI's code
You need to modify the code in the procedure.

In the whole code

public class YOUR GUI NAMEprocedureProcedure {
    public static void execute(Entity entity) {
        if (entity == null)
            return;
        if (entity instanceof Player _player && _player.containerMenu instanceof Supplier _current && _current.get() instanceof Map _slots) {
            ((Slot) _slots.get(0)).remove(1);
            _player.containerMenu.broadcastChanges();
        }
    }
}



((Slot) _slots.get(0)).remove(1);

I'll erase that part
Slot slot = (Slot) _slots.get(0);
if (slot.hasItem()) {
slot.getItem().shrink(1);

Add the .

If you don't want it to go away too soon
Please add wait to the procedure.

procedure.
https://imgur.com/UELeYNM

ALL CODE

https://imgur.com/iCeVEfL

You could make two identical blocks. One with the inventory. Each tick one replaces the other. That should destroy the item in the block with inventory but it might lag.

You could alternatively have a dispensor drop the item on the block and kill entity type item at x y z or x y+1 z.