The line feed code in the Text property of CuiInputFieldComponent is not reflected.
Is there something wrong with the settings?

[ChatCommand("cui.test")]
void ChatCommandCuiTest(BasePlayer player, string command, string[] args) {
	var elements = new CuiElementContainer();

	var mainPanel = elements.Add(new CuiPanel {
		Image = {
			Color = "0.0 0.0 0.0 1.0"
		},
		RectTransform = {
			AnchorMin = "0.4 0.4",
			AnchorMax = "0.6 0.6"
		},
		CursorEnabled = true,
		KeyboardEnabled = true
	});

	var inputPanel = elements.Add(new CuiPanel {
		Image = {
			Color = "0.4 0.4 0.4 1.0"
		},
		RectTransform = {
			AnchorMin = "0.0 0.10",
			AnchorMax = "1.0 1.00",
			OffsetMin = "0 0",
			OffsetMax = "0 0",
		},
	}, mainPanel);

	elements.Add(new CuiElement {
		Parent = inputPanel,
		Components = {
			new CuiInputFieldComponent {
				Align = TextAnchor.MiddleCenter,
				LineType = UnityEngine.UI.InputField.LineType.MultiLineNewline,
				Text = "1\n22\n333\n4444",
				Command = "",
			}
		}
	});

	elements.Add(new CuiButton {
		Button = {
			Close = mainPanel,
			Color = "1.0 1.0 1.0 0.2"
		},
		RectTransform = {
			AnchorMin = "0.4 0.00",
			AnchorMax = "0.6 0.10"
		},
		Text = {
			Text = "Close",
			FontSize = 9,
			Align = TextAnchor.MiddleCenter
		}
	}, mainPanel);

	CuiHelper.AddUi(player, elements);
}

You're not initializing all properties of the components

All initialized, but no line breaks.

elements.Add(new CuiElement {
	Parent = inputPanel,
	Components = {
		new CuiInputFieldComponent {
			Align = TextAnchor.MiddleCenter,
			LineType = InputField.LineType.MultiLineNewline,
			Text = "1\n22\n333\n4444",
			Command = "",
			Autofocus = true,
			CharsLimit = 0,
			Color = "0.0 0.0 0.0 1.0",
			Font = "RobotoCondensed-Regular.ttf",
			FontSize = 12,
			HudMenuInput = false,
			IsPassword = false,
			NeedsKeyboard = true,
			ReadOnly = true,
		}
	}
});