Apparently, Prism Launcher chose to adhere to the idiotic principle of the hidden “trashbin”, .Trash-$(uid), invented by Ubuntu. Even though it’s based on QT. This can’t be disabled. It accumulated 139 GB of literal Trash, fully replaceable, over time. Just … why? There’s even an open issue about this, for over a year, referenced multiple times. I guess I have another point on my agenda.
Depending on your file manager, you may be able to hold Shift while triggering the delete to get a hard delete.
Shift+Del is pretty much standardized as the keyboard shortcut. And here on KDE, I can hold Shift while clicking the “Move to Trash” menu entry, too (well, it actually replaces the menu entry with one for permanent deletion, but that’s effectively the same).