[DiapDealer]

I don't HAVE a keyboard with a different physical layout to fully test things out with ... but when I change my keyboard layout to French (or French (alternative)) in Ubuntu's system settings, my standard keyboard is able to type many characters with various diacritical marks directly into Sigil: including the ô character.

So far as I can tell. the custom-built Sigil that I packaged up for everyone seems to be supporting non-US keyboard layouts like it's supposed to.

I'm not 100% certain, of course, since more and more aspects of Qt5 OS integration seems to be being farmed out to plugins with each new release. For instance: with Qt 5.1, I had to include the new platformthemes plugin (which didn't exist separately in 5.0.x) in order for the various file-type icons to be displayed within Sigil's Book Browser on Linux.