I would expect that disposable VMs in Qubes provide the same set of Firefox features for all Qubes users. Unless you modified your browser in some way (and unless screen resolutions are different), our fingerprints should just coincide. However, every time I check the fingerprinting in Qubes, I get the result that I am unique among millions (amiunique) / hundreds of thousands (panopticlick) of users. It happends both on Debian and on Fedora. How is this possible? Do you get the same results?
Well, I have to admit that I have installed PrivacyBadger and HTTPS Everywhere, but they do not seem to be important:
List of plugins: none
P.S. I do know that for actual defense from the fingerprinting one should use Whonix with Tor Browser. It does show that I am not unique.