Thanks for your replies which proved to be very useful - for me.
So, Sigil has nothing to do with this and I am happy to get this confirmation. DiapDealer's build is faultless about French keyboard(and other points).
So, I must now squarely (better roundly) face my belly button.
After a second examination (better now than never) I came to realize that I have with Sigil a -slightly- different French keyboard version of the one I use everyday (
clavier alternatif français) on my Linux. There is of course a general agreement on most of the keys but also some differences, among them this elusive ô.
With the Sigil keyboard I type directly ô using together alt+P (just found!!...)
With my regular keyboard, I must type two keys, the acccent first, then the letter.
There are like that some devious differences that it would be tedious to point here which I did not understand until now and that I will begin to learn.
