This is what Robin over at Ardour.org stated:
Originally Posted by Robin Gareus
There are some statistics from “new version checks” from official versions from ardour.org and Linux users have a slight edge. That does not include all the versions from linux-distros (who disable version check calls to ardour.org ).

Ubuntu alone has 74481 installs and that’s only from users who agreed to submit stats.

As of today, official stats say 43% Linux, 42% Window, 15% Mac. Yet by factoring in Ubuntu alone it’s more like 75%, 18%, 5%. and that doesn’t include Debian, KXStudio, AVlinux, Arch, etc