OK, you got me Vlad.
In my defense, I had looked for a forum on the DXO home page. Didn't find it where I expected, at the top menu bar, or under "support" where most folks put it. On second look I see it now, buried in the fine print at the bottom of the page.
And believe it or not, "U2U" is a term I've never heard. So I Googled "U2U forum" and was led down a bunch of blind alleys.
Anyway, I registered a couple hours ago. Still waiting for my "activation link."