If you put a Tubus Tara lowrider rack on, there's only one tube at the dropout, running from top left to bottom right on your photo. The rack also has a subsidiary eyelet on the upper side of the tube to take the displaced mudguard stays without having to share a bolt. You may need a short spacer to clear the fork blade, but it should be fairly straightforward.
I used one with discs on a Singular Peregrine, but on a quick glance I don't have any photos with the area of interest unobstructed by panniers.
The other option would be an
over-the-wheel rack, like a small rear.