Nope. If you're using Qubes you are (as far as an ad network is concerned) a young middle to upper class white male with an interest in technology and computer

Nope. If you're using Qubes you are (as far as an ad network is concerned) a young middle to upper class white male with an interest in technology and computer security who probably lives near the Bay Area or another tech hub (depending on GeoIP). That's exactly what an advertiser would be tracking you to find out, and you just put it in the user agent string. The only way to defeat browser fingerprinting is for everyone (or a lot of people including you) to use exactly the same version of the same browser on the same platform on the same device configured the same way. Even the, which browser-device-screen resolution-version cohort you are part of probably says a lot about your demographic. It's easy to hide in 2560x1440 Macs running latest Chrome under Yosemite. Not so much on Ubuntu Phone in middle America.