Remove semi-transparent background and border from items in QComboBox / QAbstractItemView

Thyringer

How do I remove this predefined semi-transparent background and border from items in QComboBox / QAbstractItemView? The whole thing is particularly noticeable since I added a little more space (padding) on the left and right. I've already tried overriding all properties; but only found out that I can change the color with "selection-background-color", but not remove the transparency.
Ultimately, I just want a flat design.

For easier understanding, here is the code (inside a Python format string):

	QComboBox {{
		background-color: #FFF;
		border: none;
		color:#3C3C3C;
		font-size: {design.font_size};
		height: {design.width}px;
		padding: 0 {design.padding}px;
	}}
	
	QComboBox:editable {{
		background: #FFF;
	}}

	QComboBox QAbstractItemView {{
		border: 1px solid {ac};
		font-size: {design.notepad_font_size};
	}}
	
	QComboBox QAbstractItemView::item {{
		border: none;
		color: #3C3C3C;
		height: {design.width}px;
		padding: 0 {design.padding}px;
		selection-background-color: #F29100;
	}}
	
	QComboBox QAbstractItemView::item:hover, QComboBox QAbstractItemView::item:selected {{
		background-color: #F29100;
		border: none;
		selection-color: #FFF;
	}}

Thyringer

I have the same problem with the QListWidget, but I was able to switch off this annoying background by specifying setFocusPolicy(Qt.NoFocus). Unfortunately, this doesn't work with my drop-down list:

def DropDownList(*items: str) -> QComboBox:
	list = QDropDownList(*items)
	list.setFocusPolicy(Qt.NoFocus)
	view = list.view()
	view.setEditTriggers(QAbstractItemView.NoEditTriggers)
	view.setFocusPolicy(Qt.NoFocus)
	return list