Resizing Firefox > v140 doesn't work anymore

[branneman]

Since the update to v140, Firefox has changed the way it renders the window and does resizing (probably because of the vertical tabs feature), the header bar has also changed again. Now Rectangle won't resize any Firefox window anymore. All other apps still work fine.

Rectangle recognises it can't resize firefox, because it has disabled all options in the menu as well. When I press the shortcuts, it just gives an error sound.

macOS version: Sequoia 15.5 Rectangle version: 0.88 (94)

To reproduce, install Firefox v140 and latest Rectangle on a Mac.