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I would have guessed they were for mudguards but it's got eyelets at the dropouts for that and they do look nicely reinforced.
Doing a bit of research I think it's the same/similar to the fork off a 2011 Trek Portland which does take low-riders:
https://archive.trekbikes.com/gb/en/2011/trek/portland#/uk/en/2011/trek/portland/details
Excellent option. Clearance might be your only issue but that bike was specced with 28s so I'm sure it'd be possible to squeeze a 30 or 32 in at least. Probably don't load it up with too much weight though.
Looks like Triton have a couple of carbon straight steerer disc forks:
https://www.tritoncycles.co.uk/rahmen-gabeln-c6/rigid-forks-c51/bontrager-satellite-carbon-700c-disc-fork-p21418
https://www.tritoncycles.co.uk/frames-forks-c6/rigid-forks-c51/fx-3-disc-carbon-fork-p20757
If anyone has a ~400mm A2C QR disc fork for sale (steel or carbon or anything) for under £50 posted, give me a shout, I might be interested