Oh, good grief. So I make the account, and click on the button that looks like it should be the account settings. It directs to another website (“Club Ubisoft”) which doesn’t share the login information. That turns out to be where you update some sort of settings, but not the language. After some Googling, I find that there’s a third totally separate website (“Account management”) that appears to not be linked from Uplay. Of course it too requires a separate login.
On that site I’ve located the widget that can be used to update the language, but I can’t change it without giving Ubisoft personal information that I would never give them. Try to change the language and save, and it gives an error message requiring filling in e.g. gender. (Everything about this site is so amateurish that it’s clearly a data breach waiting to happen at any moment; they will get nothing except my email address).
But at least visiting this hidden page allowed me to untoggle the “please send me spam about exclusive offers” checkbox that I was not asked up front about during the account creation process.
Throughout this, all but one of these separate websites are complaining that I haven’t verified my email even though I did that first thing. I sure hope they don’t all require separate email verification, but at this point I would not be surprised.