Well, you could open up an issue here
But since we use the project from here
and what you noticed is present also with that theme, is better to contact the developer of it and see if there is something that can be done.
There was not much to capture from FF and Wacom. Probably needs some debugging. Anyway, i wonder about in what workflow would be efficient to use the Stylus with FF, because it might not get the attention to be fixed as you would like.
Some people even complained about the fact that for instance in LibreOffice, VLC and VirtualBox Manager the Stylus is funky, and you need to use the environment variable:
export QT_XCB_TABLET_LEGACY_COORDINATES=1
i still don’t find it efficient for use in non drawing applications …