I'm sure someone will correct me if I'm wrong, but the racks that attach down by the axle (eg Pelago, Metro etc) shouldn't be affected by the straightness of the fork. Mid-rack mounts such as the Pizza rack might give you more grief, but from what I can see there's still a bit of anterior/posterior adjustment in terms of the mid-fork mounting. Plus if you use P-clips that'll negate some of the issues with having a straight fork anyway.
Only if your straight fork is simple straightforward (no pun intended). I couldn't fit my pelago rack on my mash work because the end bits have a bit of a lip preventing the fitting to stay upright. It works but not ideal...
I'm sure someone will correct me if I'm wrong, but the racks that attach down by the axle (eg Pelago, Metro etc) shouldn't be affected by the straightness of the fork. Mid-rack mounts such as the Pizza rack might give you more grief, but from what I can see there's still a bit of anterior/posterior adjustment in terms of the mid-fork mounting. Plus if you use P-clips that'll negate some of the issues with having a straight fork anyway.