Both of my S5's did/do it, same with Q7. Sometimes to correct it I do a series of high speed braking (get up to 50 or so, slam on brakes, repeat). Learned that when my C6 Corvettes had same issue. Usually works.

Maybe you should RTM and properly bed your brakes. It's a side effect of brembo style brakes and occurs on most if not all cars I've driving with them. Try doing a 40-0mph stop by slamming on the brakes with full force a few times. This will bed the brake pads and help quite a bit. There's a similar discussion in the SQ5 subforum with the above solution.

Our brakes squeal also. At 13,000 miles now, not sure when it started. My wife says it's worse when the Q7 is cold, and gets better as it warms up.
My A6s never had this issue.

My Q7 was less then 10k miles when the rotors warped; Car was NOT driven aggressively at all.
The dealer agreed to replace rotos and pads but not without blaming me for the issue.

My other car is a 2013 A6 that also had warped rotors at about 20k. I went aftermarket and put Zimmerman rotors on it and now it has 50k miles and zero issues.

I may be wrong but I feel Audi uses poor quality parts on their brake systems.

Myth - brake rotors do not warp.

Yeah, pad deposits on the surface of the rotors give the same sensation as the rotor itself warping. Very common mistake. I also recommend using a different pad. OEM pads are rather harsh on the rotors. I prefer something a little softer with less brake dust.

I'm amazed how little dust there is with ours...of all the euros cars I've owned over the years, the 7's are some of the best.

Brake rotors can be manufactured out of tolerance/round, causing squealing, shudder in the wheel when braking at speed etc.
Brake rotors can warp when extremely hot, then directly exposed to cold water...some drive right into a car wash or take a cold hose to them right after very aggressive driving.

Our '17 with 12k miles that has been mostly driven in plenty of stop & go city traffic with only occasional highway have had squeal-free and dust-free brakes. I'm actually quite amazed at this considering how large the rotors are and how relatively heavy the Q7 is compared to our past Audis. Our SQ5 and RS7 both had extremely noisy and dust-heavy brakes. After each wash, both cars would have nasty brake-dust covered wheels in less than a week. The Q7 on the other hand has not only be silent but can go for well over a month with dust-free wheels that I'd actually have to get the car washed because the body would get dirtier from water spots and bird crap during the that time. This is the first and only car I've ever owned that's like this.

I hope I don't jinx myself, but so far 2,500 miles with no squealing and not much brake dust at all..

12,000 and no squealing or brake dust.