Thanks for your report. I can't reproduce it, though.
Whether the layout is "French (alt., Latin-9 only)" or "Swedish" I can type the dead_circumflex symbol followed by u, and get û. For me that works also with Firefox.
Which physical keys are you using to type dead_circumflex? To access that symbol on "French (alt., Latin-9 only)" I need to hold <AltGr>+<Shift> while pressing the key to the very right at the third row (to the left of the Return key).
Thanks for your report. I can't reproduce it, though.
Whether the layout is "French (alt., Latin-9 only)" or "Swedish" I can type the dead_circumflex symbol followed by u, and get û. For me that works also with Firefox.
Which physical keys are you using to type dead_circumflex? To access that symbol on "French (alt., Latin-9 only)" I need to hold <AltGr>+<Shift> while pressing the key to the very right at the third row (to the left of the Return key).