It seems when there's a line break in the text, the width of tooltip is calculated as if there's no break.

The problem can be seen by the following code.

ToolTip.text: "<p><b>Title</b></p><p>Line Text Text Text Text<br><p>Line Text Text Text Text<br>"

or

ToolTip.text: "Title \n Text Text Text Text \n Text Text Text Text"

This seems to be a regression bug that happened between Qt5.13.2 (Good) and Qt5.14.0 (Bad). See qtbug91086-5-13-2-good.png.

How to reproduce :
Use qtbug91086.zip