I use a Tubus Logo on my Nomad in back for touring, not sure if the M6 fit or if I drilled the rack to make it fit. I use the Logo for most of my touring, but do not use it for around town general use when at home because at home I want a wider platform. Touring, platform width is unimportant to me and I like the stiffness of the logo. I also use my Logo on my Sherpa for touring. And when I owned a Long Haul Trucker, also used that rack on that bike for touring.
I use a different rack on my Nomad for riding around home, that rack I drilled to M6. But I would not recommend that rack, a Surly, it weighs twice as much as the Logo, is overpriced, and is not as stiff. And, it is less flexible, so it squeezes the rear dropouts inward making it harder to set the wheel in the frame because on the Nomad the lower rack mounts are wider than on most bikes because the M5 to M6 gizmos. I regretted buying the Surly a few months after buying it, but since I already owned it I still use it. I tried to cold set the rack to fit better on the wider rack mounts, had some success.
For front rack, I would not recommend the one that I used on my Nomad, so I am not citing it here.
Some of the non-Thorn front racks do not fit well on the Nomad because the mid-fork mounts are further forward than on most other bikes, thus some racks it is difficult to get the horizontal bar to be horizontal. I tried a Tubus Tara on my Nomad, did not fit well but I think some others had better success. My point is if you consider other racks, it might be best to hold the rack up to the bike in the store before you buy to see how it would look.
Photo is of my Nomad rear end with the Surly rack attached to those M5 to M6 gizmos.
