Been using that keyboard for years now on various devices, but with Ubuntu 18.04 it seems that the double quote character comes out like this: ¨ instead of like that: " ; I tried to ignore the problem as I need the international keyboard to enter french characters like é, è, ê, à but it impacts things like google search and python coding which do not recognize the ¨ ( 168 or [00A8] ¨ DIAERESIS) or the ´ ( 180 or [00B4] ´ ACUTE ACCENT) characters. So my question is how do we fix the Ubuntu Keyboard: US Intl. with dead key so that it will display the normal " (34 [0022] " QUOTATION MARK) when the quotation mark key is pressed twice (normal behaviour) or the APOSTROPHE single quote one for that matter (39 [0027] ’ APOSTROPHE) since both are located on the same US Keyboard key.
i have seen xkb in a couple of search results (1 and 2) regarding mapping keys in ubuntu 18.04. when i take a look at /usr/share/X11/xkb/symbols/us as mentioned in that second link i see line 84 starts a section of us intl with dead keys assignments. line 128 sounds like the key you are referring to:
key AC11* { [dead_acute, dead_diaeresis, apostrophe, quotedbl ] };
*note AC11 is bracketed by <>, but they make it disappear in my response if i leave them in.
i realize this isn’t an answer as to why your keyboard isn’t doing what it should, but maybe the line is incorrect or perhaps it is possible to map a different key to what you need.
Never mind, I found another way to get the neutral quote and double quote to work with that keyboard; just by pressing the quote key and holding the [right alt] gets me the normal single quote (’) and holding [shift-right alt] gets me the double quote ("). Answered my own question I guess…
I guess you got lucky with it. 
I’m British subject so prefer English UK keyboard (it has pound sign £ ) Not impossible to find in USA but not exactly easy either. I would think a French keyboard would be available through eBay Canada or from Europe? I got a cheap one ‘just in case’ something went wrong, my grandson decided laptop didn’t need the keys so USB got plugged in.
