Just as it seemed I had found the perfect keyboard for my needs, I was reminded there's always a catch : I'm French and thus need an AZERTY layout, which isn't available.

So it seemed I would have to pass on this keyboard, then I reconsidered.
Having to learn a different layout would be a pain, but I could do it.
Having to use different layouts at home and at work would be a real pain, but I could manage.
But I really need a quick access to accented letters.
US International is out, since as a programmer I just can't have my quotes as dead keys. Quote + space just will not do.
Now UK extended just might do it. AltGr + letter isn't as fast as a direct access, but it's acceptable.

Shift-Alt-Letter isn't, though.

Hence my question : does this keyboard support AltGr or is it a traditional US keyboard with two fonctionally identical Alt keys and no AltGr ?

From the factory our Deck boards come with the standard English QWERTY layout. Since this is the only configuration we offer I would suggest changing the layout of your keyboard using the operating system's localization features and then swap the keycaps around so the keycap layout matches the computer's mappings.

Thanks for the answer, although it didn't quite answer my question.

My understanding (I may be wrong) is that on European keyboards, left alt = alt, right alt (AltGr) = shift + alt, while on US keyboards both alt keys are fonctionally identical. And it's a keyboard-level mapping, not a mere OS-level key-mapping.
In other words, with a US keyboard, there's no way for the OS to treat differently left alt and right alt.
Is that correct ?
Is it the case for Deck keyboards ?

Yes that is the case. Deck keyboards come standard with a US QWERTY mapping.

I found an article on Wikipedia that may help:
http://en.wikipedia.org/wiki/AltGr_key

From that article: